A water purification apparatus and methods for cleaning the water purification apparatus

ABSTRACT

A water purification apparatus ( 300 ) capable of being cleaned at a point of care, and methods for cleaning the water purification apparatus ( 300 ) at the point of care. The water purification apparatus ( 300 ) and the methods provide an efficient use of a heater ( 302 ) for heat disinfection the water purification apparatus ( 300 ), e.g. by recirculating heated fluid to further heat the fluid. Several different cleaning programs are provided that may be utilized for cleaning different parts of the water purification apparatus ( 300 ).

TECHNICAL FIELD

The present disclosure relates to a water purification apparatus and tocorresponding methods for cleaning the water purification apparatusincluding heat disinfection and in some embodiments a cleaning agent.The present invention also relates to a computer program and a computerprogram product implementing the methods.

BACKGROUND

In treatment of patients suffering acute or chronic renal insufficiency,dialysis therapy is employed. Three general categories of dialysistherapy are hemodialysis, HD, peritoneal dialysis, PD, and continuousrenal replacement therapy, CRRT.

In hemodialysis, the patient's blood is cleansed by passage through anartificial kidney in an extracorporeal membrane system, incorporated ina dialysis machine. The blood treatment involves extracorporealcirculation through an exchanger having a semipermeable membrane(dialyzer) in which the patient's blood is circulated on one side of themembrane and a dialysis fluid, comprising the main electrolytes of theblood in concentrations close to those in the blood of a healthysubject, is circulated on the other side. Furthermore, a pressuredifference is created between the two compartments of the dialyzer whichare delimited by the semipermeable membrane, so that a fraction of theplasma fluid passes by ultrafiltration through the membrane into thecompartment containing the dialysis fluid.

CRRT is used as an alternative therapy for patients who are too ill orunstable for standard hemodialysis. It is similar to hemodialysis andmakes use of a semipermeable membrane for diffusion and to some extentconvection. It is however a slower form of blood treatment thanhemodialysis, and may be continuously ongoing from a couple of hours upto several days.

In peritoneal dialysis, dialysis fluid is infused into the patient'speritoneal cavity. This cavity is lined by the peritoneal membrane whichis highly vascularized. The metabolites are removed from the patient'sblood by diffusion across the peritoneal membrane into the dialysisfluid. Excess fluid, i.e. water is also removed by osmosis induced by ahypertonic dialysis fluid. Through these two processes, diffusion andosmotic ultrafiltration, appropriate quantities of solute metabolitesand fluid need to be removed to maintain the patient's body fluidvolumes and composition within appropriate limits.

There are various types of peritoneal dialysis therapies, includingcontinuous ambulatory peritoneal dialysis (“CAPD”), automated peritonealdialysis (“APD”), including tidal flow APD, and continuous flowperitoneal dialysis (“CFPD”).

CAPD is a manual dialysis treatment. The patient connects manually animplanted catheter to a drain, allowing spent dialysate fluid to drainfrom the peritoneal cavity. The patient then connects the catheter to abag of fresh dialysis fluid, infusing fresh dialysis fluid through thecatheter and into the patient. The patient disconnects the catheter fromthe fresh dialysis fluid bag and allows the dialysis fluid to dwellwithin the peritoneal cavity, wherein the transfer of waste, toxins andexcess water takes place.

Automated peritoneal dialysis (“APD”) is similar to CAPD in that thedialysis treatment includes drain, fill, and dwell cycles. APD machines,however, perform the cycles automatically, typically while the patientsleeps. APD machines free patients from having to manually perform thetreatment cycles and from having to transport supplies during the day.APD machines connect fluidly to an implanted catheter, to a source orbag of fresh dialysis fluid and to a fluid drain. APD machines pumpfresh dialysis fluid from the dialysis fluid source, through thecatheter, into the patient's peritoneal cavity and allow the dialysisfluid to dwell within the cavity and the transfer of waste, toxins andexcess water to take place. APD machines pump spent dialysate from theperitoneal cavity, through the catheter, to the drain. As with themanual process, several drain, fill and dwell cycles occur during APD. A“last fill” occurs often at the end of CAPD and APD, which remains inthe peritoneal cavity of the patient until the next treatment.

Both CAPD and APD are batch type systems that send spent dialysis fluidto a drain. Tidal flow systems are modified batch systems. With tidalflow, instead of removing all the fluid from the patient over a longerperiod of time, a portion of the fluid is removed and replaced aftersmaller increments of time.

Continuous flow or CFPD systems clean or regenerate spent dialysateinstead of discarding it. CFPD systems are typically more complicatedthan batch systems.

CAPD, APD (including tidal flow) and CFPD systems can employ a pumpingcassette. The pumping cassette typically includes a flexible membranethat is moved mechanically to push and pull dialysis fluid out of andinto, respectively, the cassette.

In one form of peritoneal dialysis, an automated cycler is used toinfuse and drain dialysis fluid. This form of treatment may be doneautomatically at night while the patient sleeps. The cycler measures theamount of fluid infused and the amount removed to compute the net fluidremoval. The treatment sequence usually begins with an initial draincycle to empty the peritoneal cavity of spent dialysate. The cycler thenperforms a series of fill, dwell, and drain cycles, typically finishingwith a fill cycle.

Peritoneal dialysis generally requires large volumes of dialysis fluid.Generally, at each application, or exchange, a given patient will infuse2 to 3 liters of dialysis fluid into the peritoneal cavity. The dialysisfluid is allowed to dwell for approximately 1 to 3 hours, at which timeit is drained out and exchanged for fresh dialysis fluid. Generally,four such exchanges are performed daily. Therefore, approximately 8 to20 liters of dialysis fluid is required per day, 7 days a week, 365 daysa year for each patient.

Dialysis fluids, for use in the above-mentioned treatments, havetraditionally been provided in sealed container bag, ready for use. Forexample, peritoneal dialysis is typically performed using bags withthree different concentration of dextrose. The bags are being deliveredto a patient's home as 1 liter to 6 liter bags with different dextroseconcentrations. A normal daily consumption is around 8 to 20 liters ofPD dialysis fluid. The fluid is provided in sterilized bags of sizes upto six liters, which are packed into boxes and delivered, e.g., monthly,for use to the patient's home. The boxes of fluid may be cumbersome andheavy for PD patients to handle, and consume a substantial space in aroom of their homes. The bags and boxes also produce a relatively largeamount of waste disposed of on a weekly or monthly basis.

In light of above, several problems become apparent. Shipping andstorage of the sheer volume of fluids required is space consuming.Additionally, the use of multiple prefilled bags produces wastematerials in the form of empty containers and packaging.

Sub-systems for an overall peritoneal dialysis, PD, system that createsdialysis solution at the point of use, e.g., at the PD machine aretherefore needed.

PD dialysis fluid is delivered directly to the patient's peritonealcavity. PD fluid therefore needs to have a level of sterilizationsuitable for being introduced into the patient's peritoneum. PD dialysisfluid is accordingly premixed and sterilized typically prior to deliveryto the location of use, usually the patient's home.

Also, in hemodialysis and CRRT, systems that create dialysis solution atthe point of use, e.g., at the hemodialysis machine or CRRT machine, aretherefore needed.

An overall system for hemodialysis, PD or CRRT, in some embodiments,include three primary components, namely a dialysis machine, a waterpurifier and a disposable set operating with both the dialysis machineand the water purifier. The dialysis machine is e.g. a PD cycler, ahemodialysis machine or a CRRT machine. The dialysis machine preparesdialysis fluid from purified water from the water purifier andconcentrates.

The water purifier produces purified water from e.g. tap water, at thepoint of use of the purified water.

It is of great importance that the microbial status of the waterpurifier is excellent. In order to achieve this, the water purifier hasto be cleaned and disinfected on a timely basis. Heat disinfection is asuitable method for disinfecting fluid paths of a water purifier thatproduces water to be used in dialysis. However, for heat disinfectionpower is needed and at a point of care, for example at a patient's home,power supply may be limited.

SUMMARY

In is an object of the disclosure to provide a water purificationapparatus capable to clean itself to a microbial acceptable level at thepoint of care. It is a further object of the disclosure to providemethods for cleaning the water purification apparatus at the point ofcare. In detail, it is an object of the disclosure to provide a waterpurification apparatus and methods for cleaning the same that makes useof heat disinfection and an efficient use of the heating resource in thewater purification apparatus for providing the heat disinfection.

These objects and others are at least partly achieved by the apparatusesand methods according to the independent claims, and by the embodimentsof the dependent claims.

According to a first aspect, the disclosure relates to a waterpurification apparatus for producing purified water. The waterpurification apparatus comprises a Reverse Osmosis, RO, device, arrangedto produce a purified fluid flow and a reject fluid flow. RO-devicecomprises a feed inlet, a permeate outlet and a reject outlet. The waterpurification apparatus also comprises a feed fluid path arranged with aRO-pump to pump feed fluid to the feed inlet, a heater arranged to heatthe purified fluid produced by the RO-device downstream the RO-device, afirst fluid path arranged to circulate heated purified fluid from apoint downstream the heater to a tank arranged in the feed fluid pathinside the water purification apparatus, a second fluid path arranged totransport the heated purified fluid inside the water purificationapparatus, a valve arrangement arranged to direct the heated purifiedfluid into the first fluid path or the second fluid path and a controlunit configured to control cleaning of the water purification apparatus.The control unit is configured to cause the water purification apparatusto control heating, with the heater, of the purified fluid from theRO-device and to control the valve arrangement to re-circulate theheated purified fluid in the first fluid path, until a first temperaturedependent criterion is fulfilled. The control unit is further configuredto cause the water purification apparatus to control the valvearrangement to re-direct the heated purified fluid to flow in a secondfluid path of the water purification apparatus, in response to the firsttemperature dependent criterion is fulfilled, and to control heating,with the heater, of the re-directed heated purified fluid in order tofulfil a second temperature dependent disinfection criterion for thesecond fluid path.

The water purification apparatus according to the first aspect providesefficient heating of the purified fluid from the RO-device, byrecirculating the heated purified fluid to upstream the RO-device suchthat the heated purified fluid is again heated by the heater. Therebyonly one heater downstream the RO-device is needed to heat disinfect thewhole fluid path of the water purification apparatus that need to beheat disinfected. Further, a low power consuming heater may be used forheating, whereby the household power at a point of care is notoverutilized. The water purification apparatus may comprise at least twopaths that each recirculate water to the feed fluid path. By firstheating and recirculating the water in only one of them, e.g. the onehaving the longest flow path, the whole apparatus and thus the otherflow paths will also be warmed. The recirculated water is collected in atank and thus mixed with cooler water, before being again fed to theRO-membrane. The RO-membrane may thus not be exposed to temperaturesabove 40° C. during the recirculation in the first fluid path, eventhough the permeate water is heated to a greater temperature downstreamthe RO-membrane. In one embodiment, no fresh fluid is allowed to enterthe water purification apparatus during the recirculation of heatedpurified fluid. Thereby the re-circulated purified fluid is not mixedwith fresh, colder water, but only mixed with the water already in thetank, and the heating of the purified fluid may be performed morerapidly. By redirecting the heated fluid to a second fluid path, moreparts of the fluid circuit may become heat disinfected in an energyefficient way. The second fluid path may include the RO-membrane, andthe RO membrane may thus be heat disinfected. In some embodiments, byinterrupting the recirculation when the first temperature dependentcriterion is fulfilled, and directing the heated fluid to a second fluidpath that does not include the RO-membrane, it can be avoided to exposethe RO-membrane of the RO-device for excessive heating, which maydegrade the RO-membrane, and still make use of the same heater tocontinue heating the purified fluid such that other parts of the fluidpath of the water purification apparatus may be heat disinfected withoutaffecting the RO-membrane. Further, by heating the RO-membrane, itbecomes more permeable and will let more particles through, which mightaffect the performance of downstream located components. By controllingthe heating and directing the heated purified fluid appropriately, boththe RO-membrane and downstream located components may be spared.

The inventors have discovered that some parts of the water purificationapparatus need to be cleaned less frequent than other parts. In moredetail, a permeate side of the water purification apparatus needs to becleaned more frequently, than a feed side of the water purificationapparatus and the fluid paths that lead fluid back to the feed side. Thefeed side and the permeate side are partitioned by the RO-membrane ofthe RO-device. A fully functional RO-membrane does not let bacteriathrough. Therefore, it is considered possible to disinfect the feed sideand the fluid paths that leads permeate fluid back to the feed side lessfrequently than the permeate side. The proposed water purificationapparatus is capable of directing the heated fluid to different fluidpaths, whereby different fluid paths may be cleaned with differentfrequency. The inventors have also realized that by carrying out thecleaning in different flow paths that are cleaned separately and aftereach other, it can also be assured that the heated water reaches allparts of each flow path as an appropriate pressure and/or flow rate ineach flow path can be assured, and thus controlled.

In some embodiments, a cleaning agent is distributed in the fluid pathof the water purification apparatus during the heat disinfection. Thecleaning agent is then distributed in the heated fluid and may enhancethe cleaning effect of the heated fluid.

According to some embodiments, the first temperature dependent criterioncomprises to re-circulate the heated purified fluid in the first fluidpath, until a first temperature dependent disinfection criterion isfulfilled. Thus, according to some embodiments, the first temperaturedependent criterion is a first temperature dependent disinfectioncriterion. Thus, the first fluid path might include components such asvalves, lines, an RO-membrane etc. that should be heat disinfected. Thepurified fluid is then e.g. heated to a predetermined temperature for apredetermined time, such that a disinfection criterion is fulfilled foreach component of the first fluid path that should be heat disinfected.In one embodiment, the temperature for disinfecting the RO-membrane isachieved in a last step of the recirculation. Alternatively, theRO-membrane is only warmed up to 40° Celsius, but the purified fluid isheated to 70°-95° Celsius. This because the purified fluid will be mixedwith water of lower temperatures in the tank before being pumped to theRO-membrane. The feed water will thus have a temperature of up to 40°Celsius.

According to some embodiments, the apparatus comprises a firsttemperature sensor arranged to measure a temperature of the purifiedfluid in the first fluid path, and wherein the first temperaturedependent criterion comprises to control heating, based on the measuredtemperature, of the purified fluid such that a temperature of thepurified fluid is within a range of 70-95° Celsius. The firsttemperature sensor is arranged to sense the temperature of the heatedpurified fluid downstream the heater. For example, the first temperaturesensor may be arranged to sense the temperature of the heated purifiedfluid directly after the heater. Then the temperature of the heatedpurified fluid may be easily monitored, and the effect to the heaterregulated such that the RO-membrane is not overheated or the heatedfluid starts boiling. In other embodiments, the first temperature sensoris arranged to measure the temperature of the heated purified fluid,seen from the heater, in downstream locations, in order to monitor suchthat a disinfection criterion is fulfilled.

According to some embodiments, the apparatus comprises a first flowsensor arranged to measure a flow rate of the purified fluid; andwherein the first temperature dependent criterion comprises to controlheating of the purified fluid, and pumping with the RO-pump, based onthe measured temperature and the measured flow rate, such that thepurified fluid obtains a predetermined temperature dependent flow rate.Thereby also the flow rate of the purified fluid may be regulated toachieve a certain temperature of the purified fluid. As described, whenthe RO-membrane becomes warmer, it also becomes more permeable and morefluid, and also particles, are let through. By increasing the flow rateof the RO-pump, more fluid may be forced through the RO-membrane suchthat more purified fluid may be heated faster. For example, if thepurified fluid has been heated to a high temperature, e.g. 85° C., thepower to the heater has to be lowered to not overheat the purified fluidwhen crossing the heater. However, if the flow rate of the purifiedfluid is increased, more fluid can be heated without overheating, andthe power to the heater may be reduced less resulting in a fasterheating of the total amount of the fluid that is recirculated.

According to some embodiments, the water purification apparatuscomprises a second temperature sensor arranged to measure thetemperature of the purified fluid in the second fluid path, and whereinthe control unit is configured to determine, based on the measuredtemperature, a time duration for heat disinfecting the second fluid pathwith the fluid at the measured temperature, such that a bacterialreduction criterion is fulfilled, and to control heat disinfection ofthe second fluid path based on the time duration such that the bacterialreduction criterion is fulfilled. Thus, by measuring the temperature inthe second fluid path, the fulfillment of the disinfection criterion ofsecond fluid path may be accurately monitored and controlled. Thetemperature is in one embodiment continuously monitored.

According to some embodiments, the water purification apparatuscomprises a port in fluid communication with the second fluid path, theport being arranged to be connected to a fluid line set, and wherein thesecond temperature dependent disinfection criterion is, or comprises tofulfil, a temperature dependent disinfection criterion for the port.Thereby, the fulfillment of the disinfection criterion of the port maybe accurately monitored and controlled.

According to some embodiments, the second fluid path comprises a drainpath, and wherein the second temperature dependent disinfectioncriterion is, or comprises to fulfil, a temperature dependentdisinfection criterion for the drain path. Thereby, the fulfillment ofthe disinfection criterion of the drain path may be accurately monitoredand controlled.

According to some embodiments, the first fluid path or the second fluidpath comprises a polishing-device. According to one embodiment, thepolisher-device comprises an electrodeionization unit, EDI-device,comprising a product channel and a concentrate channel. According to analternative embodiment, the polisher-device comprises a mixed bed. Thecontrol unit is configured to cause the water purification apparatus toperform a polisher-device disinfection, e.g. an EDI-device disinfection.The polisher-device disinfection comprises to control heating of thepurified fluid that will flow through the polisher-device, in order tofulfil a temperature dependent disinfection criterion for thepolisher-device, and to control the water purification apparatus tobypass the polisher-device, in response to the temperature dependentdisinfection criterion for the polisher-device is fulfilled. Thereby,the fulfillment of the disinfection criterion of the polisher-device maybe accurately monitored and controlled. After fulfillment of thedisinfection criterion of the polisher-device, the polisher-device isthereafter bypassed, to avoid that the performance of thepolisher-device is negatively affected.

According to some embodiments, the control unit is configured to causethe water purification apparatus to: control a fluid level in the tankto a predetermined level of the tank, before heating of the purifiedfluid. The fluid level is for example controlled to a low or mediumlevel, such that the heated fluid has room to expand when heated,without needing to pass fluid to the drain.

According to some embodiments, the control unit is configured to causethe water purification apparatus to perform an active cool down of anRO-membrane of the RO-device. The active cool down comprises to controlthe RO-pump to pump water from a water source to the RO-device until apredetermined cooling criterion for a reverse osmosis, RO, membrane, ofthe RO-device has been fulfilled, and control the valve arrangement todrain reject fluid from the water purification apparatus. In order toheat disinfect the RO-membrane, the RO-membrane is heated to atemperature between 70-85° C. As the RO-membrane is vulnerable to heat,the RO-membrane is cooled down such that it is exposed to a hightemperature for a time period as short as possible.

According to some embodiments, the water purification apparatuscomprises a second pump, and wherein the control unit is configured tocause the water purification apparatus to: control the second pump topump air and control the valve arrangement to direct the air past aclosed port of the water purification apparatus in order to remove waterfrom the port. Thereby, none or less fluid will flow from the port whenthe lid thereafter is opened by the user, e.g. to connect a new fluidline set.

According to some embodiments, the water purification apparatuscomprises a second pump arranged for pumping a cleaning agent such ascitric acid, wherein the control unit is configured to cause the waterpurification apparatus to: control the second pump to pump a cleaningagent into the feed fluid path and circulate the cleaning agent in areject recirculation path from the reject outlet to the feed inlet, inorder to remove scaling on an RO-membrane of the RO-device. Thereby,there is less need to pre-treat the feed water with an anti-scalingagent, or other kind of softening methods.

According to some embodiments, the heater is arranged to a permeatefluid line in order to heat the purified fluid produced by theRO-device. Thus, the heater heats the purified fluid flowing from theRO-device. This placement of the heater provides for an efficient use ofits heating capability.

According to some embodiments, a disposable line set is in fluidcommunication with the water purification apparatus, wherein the controlunit is configured to cause the water purification apparatus to cleanthe disposable line set. The cleaning may include one or several offlushing the disposable set with cold water, flushing the disposableline set with a cleaning agent such as citric acid, flushing thedisposable line set with heated fluid and/or flushing the disposableline set with heated fluid, where the heated fluid includes the cleaningagent.

According to a second aspect, the disclosure relates to a waterpurification apparatus comprising a Reverse Osmosis, RO, device,arranged to produce a purified fluid flow and a reject fluid flow. TheRO-device comprises a feed inlet, a permeate outlet and a reject outlet.The water purification apparatus also comprises a feed fluid patharranged with a RO-pump to pump feed fluid to the feed inlet, a heaterarranged to heat the purified fluid produced by the RO-device downstreamthe RO-device, a purified fluid path arranged to transport the heatedpurified fluid, and a polisher-device arranged in the purified fluidpath. A second fluid path is arranged to bypass the polisher-device andto transport the heated purified fluid past the polisher-device. A valvearrangement is arranged to direct the heated purified fluid into thepurified fluid path or into the second fluid path. The waterpurification apparatus also comprises a control unit configured tocontrol cleaning of the water purification apparatus and configured tocause the water purification apparatus to: control heating, with theheater, of the purified fluid in the purified fluid path, in order tofulfil a temperature dependent disinfection criterion for thepolisher-device; re-directing the purified fluid producing device tobypass the polisher-device, in response to the temperature dependentdisinfection criterion for the polisher-device is fulfilled and controlheating, with the heater, of the purified fluid in the second fluid pathin order to fulfil a temperature dependent disinfection criterion forthe second fluid path.

The described water purification apparatus provides a way of properlyheat disinfecting the polisher-device, without exposing it for excessiveheating that might degrade the capacity of the same. In one embodiment,the polisher-device comprises an EDI-device. In another embodiment, thepolisher-device comprises a mixed bed.

According to some embodiments, the second fluid path comprises a portarranged in fluid communication with the second fluid path, the portbeing arranged to be connected to a fluid line set, and wherein thesecond temperature dependent disinfection criterion is, or comprises tofulfil, a temperature dependent disinfection criterion for the port,and/or wherein the second fluid path comprises a drain path and whereinthe second temperature dependent disinfection criterion is, or comprisesto fulfil, a temperature dependent disinfection criterion for the drainpath.

According to some embodiments, the heater is arranged to a permeatefluid line in order to heat the purified fluid produced by theRO-device.

According to some embodiments, the water purification apparatuscomprises a heat conserving arrangement arranged to transfer heat from afluid in a first drain path and/or a fluid in a second drain path, toanother medium. fluid in an inlet path, of the water purificationapparatus. Thereby energy may be conserved, and the risk of contactingheated fluid is reduced as the drained fluid is cooled down.

According to a third aspect, the disclosure relates to a method forcleaning a water purification apparatus for producing purified water,the water purification apparatus comprises a Reverse Osmosis, RO, deviceproducing a purified fluid flow and a reject fluid flow. The methodcomprises controlling heating of the purified fluid downstream theRO-device; re-circulating the heated purified fluid in a first fluidpath from a point downstream the heater to a tank arranged in a feedfluid path upstream the RO-device, until a first temperature dependentcriterion is fulfilled; re-directing the heated purified fluid to flowin a second fluid path of the water purification apparatus, in responseto the first temperature dependent criterion being fulfilled; andcontrolling heating of the re-directed heated purified fluid in order tofulfil a second temperature dependent disinfection criterion for thesecond fluid path.

The same effects as described with reference to the water purificationapparatus may be achieved with the methods.

According to some embodiments, the first temperature dependent criterioncomprises re-circulating the heated purified fluid in the first fluidpath to the feed fluid path, until a first temperature dependentdisinfection criterion is fulfilled. Thus, according to someembodiments, the first temperature dependent criterion is a firsttemperature dependent disinfection criterion.

According to some embodiments, the controlling heating andre-circulating comprises: measuring the temperature of the purifiedfluid in the first fluid path; and wherein the first temperaturedependent criterion comprises controlling heating, based on the measuredtemperature, of the purified fluid such that a temperature of thepurified fluid is within a range of 70°-95° Celsius.

According to some embodiments, the controlling heating andre-circulating comprises: measuring a flow rate of the purified fluid;and wherein the first temperature dependent criterion comprises tocontrol heating and pumping with the RO-pump, based on the measuredtemperature and the measured flow rate, such that the purified fluidobtains a predetermined temperature dependent flow rate.

According to some embodiments, the controlling heating comprises:measuring the temperature of the fluid in the second fluid path; andwherein the method comprises determining, based on the measuredtemperature, a time duration for heat disinfecting the second fluid pathwith the fluid at the measured temperature, such that a bacterialreduction criterion is fulfilled, and controlling heat disinfection ofthe second fluid path based on the time duration such that the bacterialreduction criterion is fulfilled.

According to some embodiments, the water purification apparatuscomprises a port in fluid communication with the second fluid path, theport being arranged to be connected to a fluid line set, and wherein thesecond temperature dependent disinfection criterion is, or comprises tofulfil, a temperature dependent disinfection criterion for the port.

According to some embodiments, the second fluid path comprises a drainpath, and wherein the second temperature dependent disinfectioncriterion is, or comprises to fulfil, a temperature dependentdisinfection criterion for the drain path.

According to some embodiments, the first fluid path or the second fluidpath comprises a polisher-device, and the method comprises performing anpolisher-device comprising: controlling heating of the purified fluidthat will flow through the polisher-device, in order to fulfil atemperature dependent disinfection criterion for the polisher-device;controlling the water purification apparatus to bypass thepolisher-device, upon the temperature dependent disinfection criterionfor the polisher-device is fulfilled.

According to some embodiments, the method comprises controlling a fluidlevel in a tank arranged in the feed fluid path to a predetermined levelof the tank, before heating of the purified fluid.

According to some embodiments, the method comprises performing an activecool down of an RO-membrane of the RO-device, the active cool downcomprising: pumping water from a water source to the RO-device until apredetermined cooling criterion for the RO-membrane has been fulfilled;and controlling draining of reject fluid from the water purificationapparatus.

According to some embodiments, the method comprises pumping air past aclosed port of the purified water producing device in order to removewater from the port.

According to some embodiments, the method comprises circulating acleaning agent such as citric acid in a reject recirculation path from areject outlet to a feed inlet of the RO-device, in order to removescaling on an RO-membrane of the RO-device.

According to some embodiments, the method comprises transferring thermalenergy from a fluid in a first drain path and/or a fluid in a seconddrain path, to another medium. The another medium is for example a fluidin an inlet path of the water purification apparatus, or another fluidin a conserving element, e.g. a closed container with the another fluid.

According to some embodiment, the method comprising cleaning adisposable line set in fluid communication with the water purificationapparatus.

According to a fourth aspect, the disclosure relates to a method forcleaning a water purification apparatus for producing purified water,the water purification apparatus comprises a Reverse Osmosis, RO, deviceproducing a purified fluid flow and a reject fluid flow. The methodcomprises controlling heating of the purified fluid produced by theRO-device downstream the RO-device, directing the heated purified fluidin a first fluid path, through a polisher-device; re-directing theheated purified fluid into a second fluid path to bypass thepolisher-device, in response to a temperature dependent disinfectioncriterion for the polisher-device is fulfilled; controlling heating ofthe re-directed purified fluid; in order to fulfil a temperaturedependent disinfection criterion for the second fluid path.

According to some embodiments, the water purification apparatuscomprises a port in fluid communication with the second fluid path, theport being arranged to be connected to a fluid line set, and wherein thesecond temperature dependent disinfection criterion is, or comprises tofulfil, a temperature dependent disinfection criterion for the portand/or wherein the second fluid path comprises a first drain path, andwherein the second temperature dependent disinfection criterion is, orcomprises to fulfil, a temperature dependent disinfection criterion forthe drain path.

According to a fifth aspect, the disclosure relates to a computerprogram comprising instructions which, when the program is executed by acomputer, e.g. the control unit of the water purification apparatus,cause the computer to carry out the method according to any one of theembodiments herein.

According to a sixth aspect, the disclosure relates to acomputer-readable medium comprising instructions which, when executed bya computer, cause the computer to carry out the method according to anyone of the embodiments herein.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a front elevation view of one embodiment of a PD dialysissystem having point of care dialysis fluid production using purifiedwater from a water purification apparatus.

FIG. 2 is an elevation view of one embodiment of a disposable line setused with the system illustrated in FIG. 1.

FIG. 3 is a schematic of some functional parts of the water purificationapparatus.

FIG. 4 is a schematic of an electrodeionization device according to oneembodiment.

FIG. 5 is a schematic illustration of a of a water purificationapparatus according to a first exemplary embodiment.

FIG. 6 is a schematic illustration of a of a water purificationapparatus according to a second exemplary embodiment.

FIG. 7 is a schematic illustration of a of a water purificationapparatus according to a third exemplary embodiment.

FIGS. 8-12 illustrate steps of the cleaning method according to someembodiments.

FIG. 13 illustrates an embodiment of the water purification apparatus ingreater detail.

FIG. 14 illustrates an embodiment of a heat conserving arrangement.

DETAILED DESCRIPTION

In the following a water purification apparatus capable for beingcleaned at a point of care, where the cleaning includes heatdisinfection, and methods for performing the cleaning including heatdisinfection, will be explained. In one embodiment, a fluid line setfluidly connected to the water purification apparatus is also cleaned.

The water purification apparatus is capable of producing water for usein dialysis treatment, e.g. for mixing dialysis fluid to be used in thedialysis treatment. In some embodiments, the water purificationapparatus is capable of producing water for injection.

The water purification apparatus is in the following explained as a partincluded in a peritoneal dialysis system. However, the waterpurification apparatus may be used for producing purified water to otherkinds of dialysis systems, e.g. hemodialysis or CRRT systems, for use inproduction of dialysis fluids to be used in the hemodialysis or CRRTtreatments performed by the systems at a point of care or point of use.

Referring now to the drawings and in particular to FIG. 1, oneembodiment of a peritoneal dialysis system having point of use dialysisfluid production of the present disclosure is illustrated by system 10a. System 10 a includes a cycler 20 and a water purification apparatus300. Suitable cyclers for cycler 20 include, e.g., the Amia® orHomeChoice® cycler marketed by Baxter International Inc., with theunderstanding that those cyclers need updated programming to perform anduse the point of use dialysis fluid produced according to system 10 a.To this end, cycler 20 includes a control unit 22 having at least oneprocessor and at least one memory. Control unit 22 further includes awired or wireless transceiver for sending information to and receivinginformation from a water purification apparatus 300. Water purificationapparatus 300 also includes a control unit 112 having at least oneprocessor and at least one memory. Control unit 112 further includes awired or wireless transceiver for sending information to and receivinginformation from control unit 22 of cycler 20. Wired communication maybe via Ethernet connection, for example. Wireless communication may beperformed via any of Bluetooth™, WiFi™, Zigbee®, Z-Wave®, wirelessUniversal Serial Bus (“USB”), or infrared protocols, or via any othersuitable wireless communication technology. The control unit 22comprises a computer program comprising instructions which, when theprogram is executed by the control unit 22, cause the control unit 22and the water purification apparatus to carry out any one or several ofthe methods and programs according to any one of the herein disclosedembodiments. The instructions may be saved on a computer-readable mediumsuch as a portable memory device, e.g. a USB memory, a portablecomputer, or similar, and loaded into the control unit 22.

Cycler 20 includes a housing 24, which holds equipment programmed viacontrol unit 22 to prepare fresh dialysis solution at the point of use,pump the freshly prepared dialysis fluid to patient P, allow thedialysis fluid to dwell within patient P, then pump used dialysis fluidto a drain. In the illustrated embodiment, water purification apparatus300 includes a first drain path 384, leading to a drain 339, which canbe a housing drain or drain container. The equipment programmed viacontrol unit 22 to prepare fresh dialysis solution at the point of usein an embodiment includes equipment for a pneumatic pumping system,including but not limited to (i) one or more positive pressurereservoir, (ii) one or more negative pressure reservoir, (iii) acompressor and a vacuum pump each under control of control unit 22, or asingle pump creating both positive and negative pressure under controlof control unit 22, for providing positive and negative pressure to bestored at the one or more positive and negative pressure reservoirs,(iv) plural pneumatic valve chambers for delivering positive andnegative pressure to plural fluid valve chambers, (v) plural pneumaticpump chambers for delivering positive and negative pressure to pluralfluid pump chambers, (vi) plural electrically actuated on/off solenoidpneumatic valves under control of control unit 22 located between theplural pneumatic valve chambers and the plural fluid valve chambers,(vii) plural electrically actuated variable orifice pneumatic valvesunder control of control unit 22 located between the plural pneumaticpump chambers and the plural fluid pump chambers, (viii) a heater undercontrol of control unit 22 for heating the dialysis fluid as it is beingmixed in one embodiment, and (viii) an occluder 26 under control ofcontrol unit 22 for closing the patient and drain lines in alarm andother situations.

In one embodiment, the plural pneumatic valve chambers and the pluralpneumatic pump chambers are located on a front face or surface ofhousing 24 of cycler 20. The heater is located inside housing 24 and inan embodiment includes heating coils that contact a heating pan, whichis located at the top of housing 24, beneath a heating lid (not seen inFIG. 1).

Cycler 20 in the illustrated embodiment includes a user interface 30.Control unit 22 in an embodiment includes a video controller, which mayhave its own processing and memory for interacting with primary controlprocessing and memory of control unit 22. User interface 30 includes avideo monitor 32, which may operate with a touch screen overlay placedonto video monitor 32 for inputting commands via user interface 30 intocontrol unit 22. User interface 30 may also include one or moreelectromechanical input device, such as a membrane switch or otherbutton.

Water purification apparatus 300 in the illustrated embodiment alsoincludes a user interface 120. Control unit 112 of water purificationapparatus 300 in an embodiment includes a video controller, which mayhave its own processing and memory for interacting with primary controlprocessing and memory of control unit 112. User interface 120 includes avideo monitor 122, which may likewise operate with a touch screenoverlay placed onto video monitor 122 for inputting commands intocontrol unit 112. User interface 120 may also include one or moreelectromechanical input device, such as a membrane switch or otherbutton. Control unit 112 may further include an audio controller forplaying sound files, such as alarm or alert sounds, at one or morespeaker 124 of water purification apparatus 300.

Referring additionally to FIG. 2, one embodiment of disposable line set40 is illustrated. Disposable line set 40 is also illustrated in FIG. 1,mated to cycler 20 to move fluid within the disposable line set 40,e.g., to mix dialysis fluid as discussed herein. Disposable line set 40in the illustrated embodiment includes a disposable cassette 42, whichmay include a planar rigid plastic piece covered on one or both sides bya flexible membrane. The membrane pressed against housing 24 of cycler20 forms a pumping and valving membrane. FIG. 2 illustrates thatdisposable cassette 42 includes fluid pump chambers 44 that operate withthe pneumatic pump chambers located at housing 24 of cycler 20 and fluidvalve chambers 46 that operate with the pneumatic valve chambers locatedat housing 24 of cycler 20.

FIGS. 1 and 2 illustrate that disposable line set 40 includes a patientline 50 that extends from a patient line port of cassette 42 andterminates at a patient line connector 52. FIG. 1 illustrates thatpatient line connector 52 connects to a patient transfer set 54, whichin turn connects to an indwelling catheter located in the peritonealcavity of patient P. Disposable line set 40 includes a drain line 56that extends from a drain line port of cassette 42 and terminates at adrain line connector 58. FIG. 1 illustrates that drain line connector 58connects removably to a drain port 118 of water purification apparatus300.

FIGS. 1 and 2 further illustrate that disposable set 40 includes aheater/mixing line 60 that extends from a heater/mixing line port ofcassette 42 and terminates at a heater/mixing bag 62 discussed in moredetail below. Disposable set 40 includes an upstream water line segment64 a that extends to a water inlet 66 a (FIG. 2) of water accumulator66. A downstream water line segment 64 b extends from a water outlet 66b (FIG. 2) of water accumulator 66 to cassette 42. In the illustratedembodiment, upstream water line segment 64 a begins at a water lineconnector 68 and is located upstream from water accumulator 66. FIG. 1illustrates that water line connector 68 is removably connected to awater outlet, i.e. the product port 128 of water purifier 110.

Water purification apparatus 300 outputs purified water and watersuitable for e.g. peritoneal dialysis (“WFPD”). WFPD is water suitablefor making dialysis fluid for delivery to the peritoneal cavity ofpatient P. WFPD is for example water for dialysis or water forinjection.

In one embodiment, a sterile sterilizing grade filter 70 a is placedupstream from a downstream sterile sterilizing grade filter 70 b.Filters 70 a and 70 b may be placed in water line segment 64 a upstreamof water accumulator 66. Sterile sterilizing grade filters 70 a and 70 bmay be pass-through filters that do not have a reject line. Pore sizesfor sterilizing filter may, for example, be less than a micron, such as0.1 or 0.2 micron. Suitable sterile sterilizing grade filters 70 a and70 b may, for example, be Pall IV-5 or GVS Speedflow filters, or befilters provided by the assignee of the present disclosure. Inalternative embodiments, only one or more than two sterile sterilizinggrade filter are placed in water line segment 64 a upstream of wateraccumulator 66. The one or several sterile sterilizing grade filters maybe arranged close to the water accumulator 66, such that the fluid lineset 40 becomes easier to fold. In further alternative embodiments, thereare no sterile sterilizing grade filters in the water line segment 64 a.The sterile sterilizing grade filters may for example be replaced by oneor several ultrafilters located in the product fluid path of the waterpurification apparatus 300.

FIG. 2 further illustrates that a last bag or sample line 72 may beprovided that extends from a last bag or sample port of cassette 42.Last bag or sample line 72 terminates at a connector 74, which may beconnected to a mating connector of a premixed last fill bag of dialysisfluid or to a sample bag or other sample collecting container. Last bagor sample line 72 and connector 74 may be used alternatively for a thirdtype of concentrate if desired.

FIGS. 1 and 2 illustrate that disposable set 40 includes a firstconcentrate line 76 extending from a first concentrate port of cassette42 and terminates at a first cassette concentrate connector 80 a. Asecond concentrate line 78 extends from a second concentrate port ofcassette 42 and terminates at a second cassette concentrate connector 82a.

FIG. 1 illustrates that a first concentrate container 84 a holds afirst, e.g., glucose, concentrate, which is pumped from container 84 athrough a container line 86 to a first container concentrate connector80 b, which mates with first cassette concentrate connector 80 a. Asecond concentrate container 84 b holds a second, e.g., buffer,concentrate, which is pumped from container 84 b through a containerline 88 to a second container concentrate connector 82 b, which mateswith second cassette concentrate connector 82 a.

In an embodiment, to begin treatment, patient P loads cassette 42 intocycler and in a random or designated order (i) places heater/mixing bag62 onto cycler 20, (ii) connects upstream water line segment 64 a toproduct port 128 of water purification apparatus 300, (iii) connectsdrain line 56 to drain port 118 of water purification apparatus 300,(iv) connects first cassette concentrate connector 80 a to firstcontainer concentrate connector 80 b, and (v) connects second cassetteconcentrate connector 82 a to second container concentrate connector 82b. At this point, patient connector 52 is still capped. Once freshdialysis fluid is prepared and verified, patient line 50 is primed withfresh dialysis fluid, after which patient P may connect patient lineconnector 52 to transfer set 54 for treatment. Each of the above stepsmay be illustrated graphically at video monitor 32 and/or be providedvia voice guidance from speakers 34.

The water purification apparatus 300 is in the following described inmore detail.

Schematic of Functional Parts of Water Purification Apparatus

In FIG. 3 is a schematic of the functional parts of the waterpurification apparatus 300 according to one embodiment, including apre-treatment module 160, a reverse-osmosis (RO) module 170 and apost-treatment module 180. The water purification apparatus 300comprises an inlet port 399 for feeding water from a water source 398,e.g. a water tap, into the water purification apparatus 300, forpurification of the water. The incoming water from the water source isfed through the inlet port 399 into the pre-treatment module 160.

The Pre-Treatment Module

The Pre-treatment module 160 treats the incoming water with a particlefilter and a bed of activated carbon.

The particle filter is arranged to remove particles such as clay, siltand silicon from the incoming water. The particle filter is arranged toprohibit particles in the size of micro meter, optionally also largerendotoxin molecules, from the incoming water.

The bed of activated carbon is arranged to remove chlorine andcompositions with chlorine from the incoming water, and to absorb toxicsubstances and pesticides. In an example embodiment, the bed ofactivated carbon is arranged to remove one or several of hypochlorite,chloramine and chlorine. In a further example embodiment, the bed ofactivated carbon is also arranged to reduce organic compounds (TOC totalorganic carbon) including pesticides of the incoming water.

In some embodiments, the particle filter and the bed of activated carbonare integrated in one single consumable part. The consumable part is forexample exchanged on a predefined interval dependent on the incomingwater quality. The quality of the incoming water is for example examinedand determined by qualified people before the first use of the waterpurification apparatus 300 at a point of care.

Optionally the pre-treatment module 160 comprises an ion exchange devicefor protection of downstream located devices such as a Reverse Osmosis,RO, membrane and a polisher.

The pre-treatment module 160 thus filters the incoming water anddelivers pre-treated water to a downstream located RO-module 170.

RO-Module

The RO-module 170 removes impurities from the filtered water, such asmicroorganisms, pyrogens and ionic material from the pre-treated waterby the effect of reverse osmosis. The pre-treated water is pressurizedby a pump and forced through RO-membrane to overcome the osmoticpressure. The RO-membrane is for example a semi-permeable membrane.Thereby the stream of pre-treated water, called feed water, is dividedinto a reject stream of water and a stream of permeate water. In anexample embodiment, the reject water may be passed via a one or both ofa first reject path and a second reject path. The first reject pathrecirculates reject water back to the feed fluid path of the RO-pump inorder to be fed back into RO-device again. The recirculated reject waterincreases the feed flow to the RO-device, to get a sufficient flow pastthe reject side of the RO-membrane to minimize scaling and fouling ofthe RO-membrane. The second reject path directs reject water to drain.This makes the concentration level on the reject side to be sufficientlylow to get an appropriate, required, permeate fluid concentration. Ifthe feed water has low content of solutes, part of the drain flow canalso be directed back to the inlet side of the RO-membrane and therebyincreasing the water efficiency of the water purification apparatus 300.

The RO-module 170 thus treats the pre-treated water and deliverspermeate water to a downstream located post-treatment module 180.

Post-Treatment Module

The post-treatment module 180 polishes the permeate water in order tofurther remove ions from the permeate water. The permeate water ispolished using a polisher device such as an Electrodeionization, EDI,device or a mixed bed filter device.

The EDI-device makes use of electrodeionization for removing ions, fromthe permeate water, such as aluminum, lead, cadmium, chromium, sodiumand/or potassium etc., which have penetrated the RO-membrane. TheEDI-device utilizes electricity, ion exchange membranes and resin todeionize the permeate water and separate dissolved ions, i.e.impurities, from the permeate water. The EDI-device produce polishedwater, polished by the EDI-device to a higher purity level than thepurity level of the permeate water. The EDI has an anti-bacterial effectof the product water and can reduce the amount of bacteria andendotoxins in the water due to, among other, the electrical field in theEDI-device.

The mixed bed filter device comprises a column, or container, with amixed bed ion exchange material.

The polished water, herein also referred to as product water, isthereafter ready for being delivered from a product port 128 of thewater purification apparatus 300 to a point of use of the product water.The product water is suitable for dialysis, i.e. water for dialysis. Inone embodiment, the product water is water for injection. In an exampleembodiment, a disposable line set 40, including a drain line 56, isarranged to the water purification apparatus 300 for transporting theproduct water to a point of use. Optionally, the water purificationapparatus 300 comprises a drain port 118. The drain port 118 is in oneexample embodiment used for receiving used fluid, e.g. from a PDpatient, via a drain line 64, for further transport via a first drainpath 384 inside the water purification apparatus 300 to a drain 339 ofthe water purification apparatus 300. As a further option, the drainport 118 receives a sample of ready mixed solution for further transportto a conductivity sensor arranged in the water purification apparatus300, e.g. in the first drain path 384. The disposable line set 40 ishere arranged with a sterilized sterile filter set 70 a, 70 b, forfiltering the product water from the water purification apparatus 300 toensure a quality of the product water as of water for injection.

Thus, the product water collected in the accumulator bag 66 has passedthrough one or several sterile sterilizing grade filters of thedisposable line set 40 for removal of bacteria and endotoxins, i.e. toproduce sterile product water. According to one embodiment, the sterilesterilizing grade filters are redundant.

By collecting the sterile product water in the accumulator bag 66, thewater purification apparatus 300 and the cycler 20 are decoupled interms of pressure, so that the high pressure needed to push waterthrough the sterile sterilizing grade filters does not affect the cycler20.

EDI

In FIG. 4 a schematic of an example embodiment an EDI-device 306 isillustrated. The EDI-device 306 comprises one or more product channels306 a, two or more concentrate channels 306 b, and one or more electrodechannels 306 c. However, the EDI-device 306 is for simplicity referredto as having one product channel 306 a, one concentrate channel 306 band one electrode channel 306 c. Permeate water is fed to all thechannels via a polisher fluid path 371 b. The produced product water isoutputted from the product channel 306 a into a product fluid path 371c. The concentrate water from the concentrate channel 306 b, whichcontains ions removed from the permeate water to produce product water,is outputted to a concentrate fluid path 377 c. The electrode fluid fromthe electrode channel 306 c, which contains gas etc., is outputted to anelectrode fluid path 377 d. The concentrate water and electrode fluid isfor example passed to drain 339 or recirculated to the tank 350 forreuse. The concentrate fluid path 377 c and the electrode fluid path 377d may debouch into the same fluid path, herein referred to as theconcentrate fluid path 377 c.

Introduction to Cleaning

The control unit 112 of the water purification apparatus 300 is arrangedto set the water purification apparatus 300 in different operatingstates. The water purification apparatus 300 is arranged to act uponcommands from the cycler 20.

The water purification apparatus 300 is, when not in use but powered on,set in a standby state.

When a treatment is finished, for example a PD-treatment, the dialysismachine or cycler 20 sends a message to the water purification apparatus300 in order for the water purification apparatus 300 to set itselfready for disconnection of the disposable line set 40 and to make sure aport lid 401 (the port lid 401 covering and the product port 128 anddrain port 118 from the outside, and at the same time connects theproduct port 128 and the drain port 118) is closed. The waterpurification apparatus 300 then checks that the port lid 401 for theports 118, 128 is closed. For example, may a sensing circuit comprisinga contact sensor 345 (see FIG. 13), such as a Hall-sensor, be present ina wall of the water purification apparatus 300, to sense the closing ofthe port lid 401, and send a closed lid signal to the control unit 112if the port lid 401 is closed.

It is of great importance that the microbial status of RO module 170 andthe post-treatment module 180 of the water purification apparatus 300 isexcellent. In order to achieve this, the water purification apparatus300 runs cleaning programs on a timely basis. The heat disinfectionprograms included in the cleaning are in some embodiments based on thefollowing principle. Heating aims at preventing growth of bacteria onthe internal surfaces of the fluid path of the water purificationapparatus 300. In order to achieve a sufficient reduction of organisms,the heat disinfection is in some embodiments based on the “A0 concept”.The A0 concept will be explained in more detail in the following. The A0concept defines the dose of heat disinfection. “Fluid path or flow pathof the water purification apparatus 300” according to one embodimentincludes all the different flow paths or fluid paths making up the ROmodule 170 and the post-treatment module 180 of the water purificationapparatus 300. Thus, in this embodiment, the pre-treatment fluid pathconnecting the inlet port 333 with the water tank 350, and a tank airvent line 325 (overflow connection) to drain 339, if any (See FIG. 13),are not heat disinfected.

The cleaning programs can either be scheduled for automatic start ormanually started from a user interface menu or service interface of thewater purification apparatus 300. After an interrupted cleaning program,the water purification apparatus 300 will go back to the state standby,where it will be noted that there still need to be performed a cleaningand restart the program.

Some parts of the water purification apparatus 300 are part of theRO-membrane feed side and of fluid paths that leads permeate fluid backto the feed side. The RO-membrane feed side includes the tank 350, thefeed fluid path 391, the RO-pump 450, the parts of the RO-deviceupstream the RO-membrane 324 and reject fluid paths 389, 385 b and thecomponents therein. These parts need to be cleaned frequently. However,between these parts and the permeate side stands the RO-membrane. Thepermeate side includes the fluid paths that lead to the ports 118, 128and the first drain path 384 and the components therein, i.e. the fluidpaths that do not lead permeate fluid back to the feed side. A fullyfunctional RO-membrane does not let bacteria through. Therefore, it isconsidered possible to disinfect these parts of the water purificationapparatus 300 (thus the RO-membrane feed side and of fluid paths thatleads permeate fluid back to the feed side) less frequently than thepermeate side. The disinfection frequency need however be such that thebacterial growth is kept acceptable low. E.g. no biofilm is tolerated inthe fluid path of the RO module 170 and the post-treatment module 180 ofthe water purification apparatus 300. But, as long as this can beachieved, all parts except the parts leading directly to the productport 128, are considered to require less frequent disinfection than theproduct port 128 itself and the parts leading directly to the productport 128.

The first drain path 384 of the water purification apparatus 300 may bein contact with patient fluid, possibly containing e.g. proteins, fibrinmaterial and other substances that may grow onto the walls of the fluidpath, for example when used dialysis fluid is passed via the first drainpath 384 to drain 339. Hence, even if this part only receives fluid,bacteria can grow and possibly climb up the first drain path 384 to thecassette 42 of the disposable line set 40. It is therefore importantthat this part of the water purification apparatus 300 is also cleanedfrequently. According to some embodiments, the ports 118, 128 and thefirst drain path 384 are cleaned and/or disinfected after everytreatment to prevent growth.

According to some embodiments, the water purification apparatus 300 isprogrammed to know and to schedule when and how to run the differentdisinfection programs. In order to, as far as possible, protect thecomponents of the water purification apparatus 300, for increasedreliability, and to prevent bacterial growth, a number of differentcleaning and disinfection programs are provided by the waterpurification apparatus 300. Some of these embodiments will be explainedin the following. Note that FIGS. 5-7 are conceptual drawings that onlyillustrates parts of the water purification apparatus 300 that arerelated to the proposed technique. A more detailed illustration of anexemplary water purification apparatus 300 is provided in relation toFIG. 13.

During cleaning of the water purification apparatus 300, a cleaningagent such as citric acid is in some embodiments introduced into theflow of water, and therefore it is here referred to “fluid” instead ofpurely water. The purified fluid flow is thus in some embodiments apurified water flow, and the reject fluid flow a reject water flow.

FIG. 5 illustrates a first exemplary embodiment of a water purificationapparatus 300. Further below, a method for cleaning the fluid path ofthe water purification apparatus 300 in FIG. 5 during a generaldisinfection will be explained, with reference to the flowchart of FIGS.8-12.

The differences in line style of the fluid paths of FIG. 5 illustratethe main flows in a first fluid path (thicker lines) and a second fluidpath (dash double dot line), during a general disinfection.

With reference now to FIG. 5, the RO-device 301 is arranged to produce apurified fluid flow and a reject fluid flow. In greater detail, theRO-device 301 comprises a feed inlet 301 a, a permeate outlet 301 b anda reject outlet 301 c. The RO-membrane 324 separates the feed inlet 301a and the reject outlet 301 c, from the permeate outlet 301 b. A feedfluid path 391 is connected to the feed inlet 301 a, in order totransport feed fluid to the feed inlet 301 a. The feed fluid path 391 isarranged with a tank 350 for collecting fluid, and a RO-pump 450,arranged to pump feed fluid to the feed inlet 301 a. The RO-pump 450 isarranged downstream the tank 350. The RO-pump 450 is configured to becontrolled to a certain pump rate corresponding to a certain flow rateof the permeate fluid. As the permeability of the RO-membrane 324increases as the temperature of the feed fluid increases, therelationship between the pump rate and the flow rate is dependent on thetemperature of the feed fluid, and thus the temperature of theRO-membrane 324. In one alternative embodiment, the tank 350 is notpresent.

The water purification apparatus 300 further comprises a purified fluidpath 371, connected to the permeate outlet 301 b and to the product port128, in order to transport purified fluid from the permeate outlet 301 bto the product port 128. The purified fluid path 371 comprises thepermeate fluid path 371 a, a polisher fluid path 371 b and a productfluid path 371 c. The polisher fluid path 371 b comprises apolisher-device 306, for example an EDI-device or a mixed bed filterdevice. A bypass path 371 d is arranged to bypass the polisher device. Athree-way valve 305 c is arranged to be controlled by the control unit112 to direct the permeate fluid flow selectively to either into thepolisher-device 306, or into the bypass path 371 d in order to bypassthe polisher-device 306. A first drain path 384 is connected to thedrain port 118 and to the drain 339, in order to pass fluid from thedrain port 118 to the drain 339. The first drain path 384 here embodiesthe part of a cycler drain path that is present inside the waterpurification apparatus 300. The first drain path is arranged for exampleto transport drained PD-solution from the patient to the drain 339 ofthe water purification apparatus 300.

The water purification apparatus 300 is further arranged with a heater302 arranged to heat the purified fluid produced by the RO-device 301downstream the RO-device 301. The heater 302 may for example include aheating element. A first recirculation path 381, is arranged tocirculate heated purified fluid from a point downstream the RO-device301 and downstream the heater 302, to the feed fluid path 391, insidethe water purification apparatus 300. The first recirculation path 381is in some embodiments referred to as a first fluid path. The heatedpurified fluid is here recirculated to the tank 350 and again fed to thefeed inlet 301 a of the RO-device 301. However, the heated purifiedfluid is alternatively recirculated directly to the fluid line upstreamthe RO-pump 450.

Initially, before the heating included in the cleaning program isstarted, the fluid level in the tank 350 may be controlled to apredetermined level of the tank 350. This may be achieved by monitoringthe fluid level in the tank, and controlling the inlet valve 332 and/orthe tank valve 328 (see FIG. 13).

The reject flow is feed back to the feed fluid path 391 via a firstreject path 385 b. The first reject path 385 b is connected with, and influid communication with, the reject outlet 301 c and the feed fluidpath 391. A second reject path 389, is connected with, and in fluidcommunication with, the reject outlet 301 c and here the tank 350.However, the second reject path 389 is alternatively connected with andin fluid communication with the feed fluid path 391. A second drain path388 is arranged to feed reject fluid from the reject outlet 301 c to adrain 339. A three-way valve 305 b is arranged to selectively direct thereject flow into either the second reject path 389 or into the seconddrain path 388. A constant flow device 318 is arranged to control theflow rate in the second reject path upstream the three-way valve 305 b.The described reject flow arrangement controls the balance between thepermeate flow, the reject flow and the pump rate of the RO-pump 450,dependent on the permeability of the RO-membrane 324.

The water purification apparatus 3000 comprises a second recirculationpath 375 arranged with a flow control device 305 a. In one exampleembodiment, the second recirculation path 375 is referred to as a secondfluid path. The second recirculation path 375 is arranged to transportthe heated purified fluid inside the water purification apparatus 300.In an exemplary embodiment, the second drain path 388 is also referredto as a second fluid path.

The control unit 112 is configured to control cleaning and in particulardisinfection of the water purification apparatus 300. This means tocontrol cleaning of all, or parts of, the parts of the fluid path of theRO module 170 and post-treatment module 180 of the water purificationapparatus 300 that are in contact with fluid. A fluid path is here meantto include tubes, lines, channels, inside of apparatuses, ports, thetank, components such as valves, control devices etc. of the waterpurification apparatus 300.

The control unit 112 is configured to cause the water purificationapparatus 300 to control heating, with the heater 302, of the purifiedfluid from the RO-device 301. The heater 302 comprises for example aheating rod. In one example embodiment, part of the permeate fluid path371 a is wound around the heating rod, in order to heat the purifiedfluid in the permeate fluid path 371 a efficiently. Alternatively, theheater 302 comprises a heat exchanger, arranged to exchange heat betweena heating medium and the fluid in permeate fluid path 371 a. The heater302 is in one embodiment configured to heat the purified fluid with acertain heating rate. By controlling the power to the heater 302, andthus the power of the heater, the heating rate of the heater 302 can beregulated. The heating rate is however also dependent on the flow rateof the purified fluid.

A valve arrangement 305 is arranged to direct the heated purified fluidinto the first fluid path or the second fluid path. The valvearrangement 305 comprises for example, but not limited to, one orseveral of: the flow control device 305 a, the three-way valve 305 b, athree-way valve 305 c and a product water valve 305 d.

The water purification apparatus 300 may comprise one or severaltemperature sensors, e.g. a first and a second temperature sensor.

In FIG. 5 a permeate temperature sensor 303 is arranged to measure atemperature of the purified fluid, thus the permeate fluid, in thepermeate fluid path 371 a downstream the heater 302. When the heatedpermeate fluid is directed to the first recirculation path 381, thetemperature of the heated permeate indicates the temperature of thefluid in the first recirculation path 381.

Furthermore, a product fluid temperature sensor 313 is arranged tomeasure the temperature of the product fluid, thus the temperature ofthe fluid in the product fluid path 371 c.

A flow sensor 410 is arranged to measure a flow rate of the purifiedfluid. The flow sensor 410 is here arranged to the permeate fluid path371 a and is arranged to measure the flow rate of the permeate fluidfrom the RO-device 301. The flow sensor 410 is arranged downstream thepermeate outlet 301 b, and upstream the heater 302, for example directlydownstream the RO-device 301.

For cleaning the water purification apparatus 300, the control unit 112is configured to control the valve arrangement 305 to re-circulate theheated purified fluid in a first fluid path, e.g. the firstrecirculation path 381, until a first temperature dependent criterion isfulfilled. The first temperature dependent criterion comprises forexample a time duration for the re-circulation, or a predeterminedtemperature to be achieved during the re-circulation. For example, thefirst temperature dependent criterion comprises to control heating,based on the temperature measure by the first temperature sensor, of thepurified fluid such that the temperature of the purified fluid is withina range of 70°-95° Celsius. According to one embodiment, the firsttemperature dependent criterion comprises to control heating, based onthe temperature measure by the first temperature sensor, of the purifiedfluid such that the temperature of the purified fluid is within a rangeof 70°-95° Celsius for a predetermined time period, e.g. 5, 10, 15 or 20minutes. As the heated purified fluid is recirculated to the tank 350,the heated purified fluid will be mixed with cooler fluid in the tank350, and the temperature of the fluid in the tank 350 will in oneembodiment not go beyond 40° Celsius. The temperature of the RO-membrane324 will thus not go beyond 40° Celsius as the RO-membrane 324 is warmedby fluid being passed through the RO-membrane fed from the tank 350,which will spare the RO-membrane 324. In one embodiment, the firsttemperature dependent criterion comprises to control heating of thepurified fluid, and pumping with the RO-pump 450, based on the measuredtemperature and the measured flow rate of the purified fluid, such thatthe purified fluid obtains a predetermined temperature dependent flowrate. Thus, as the temperature of feed fluid is increased, as it is amix of heated re-circulated purified fluid and re-circulated rejectfluid, the temperature of the RO-membrane 324 also increases. Theincreased temperature of the RO-membrane 324 makes it more permeable,and more fluid can be forced through the RO-membrane 324. Theconsequence is decreased purification by the RO-device 301, but as thewater purification apparatus 300 is in a cleaning mode, it can betolerated. In one embodiment, also the RO-membrane is heat disinfectedup to a range of 70°-95° Celsius for a predetermined time period, e.g.5, 10, 15 or 20 minutes. However, according to some other embodiments,the temperature of the RO-membrane 324 should preferably not go beyond acertain temperature, e.g. 40° Celsius. The first recirculation path 381is in one embodiment the longest and/or outermost recirculation path ofthe fluid recirculation paths, such that the whole water purificationapparatus is heated while recirculating heated water in the firstrecirculating path 381 which will speed up the subsequent heatdisinfection of the remaining fluid paths.

The temperature of the RO-membrane 324 essentially corresponds to thetemperature of the permeate fluid before it is heated by the heater 302,and may be estimated by monitoring the power needed by the heater 302 toreach a certain temperature of the heated purified fluid, measured bythe permeate temperature sensor 303, see Equation (1) below. In anexample embodiment, the power to the heater 302 is set to a certainpower level, e.g. a maximum level tolerated by the water purificationapparatus 300, and the purified fluid is heated to a predeterminedtemperature (corresponding to a predetermined RO-membrane temperature)while the heater 302 is powered with the certain power level. When thepredetermined temperature of the RO-membrane, alternatively the purifiedfluid, has been reached, the power to the heater 302 is reduced, inorder to not overheat the RO-membrane and/or cause the fluid startboiling. The predetermined temperature of the RO-membrane is in oneembodiment 40 Celsius. In an alternative embodiment, the predeterminedtemperature of the RO-membrane is 70°-85° Celsius. However, as the poweris reduced, the pump rate of the RO-pump 450 may simultaneously beincreased, in order to heat the purified fluid more rapidly to thepredetermined temperature. The flow rate of the purified fluid is thenmonitored, measured by the flow sensor 410, in order to obtain apredetermined flow rate of the purified fluid that is temperaturedependent and correlated with the power to the heater 302. The pumpingrate of the RO-pump 450 is thus controlled based on the flow rate of thepurified fluid, and the power fed to the heater 302.

The temperature of the RO-membrane 324 may be calculated as follows:

$\begin{matrix}{T_{RO} = {T_{permeat} - \frac{P}{Q \cdot {cp}}}} & {{Equation}\mspace{14mu} (1)}\end{matrix}$

where P is the power [W] fed to the heater 302, Q is the flow rate [l/s]measured by the flow sensor 410, T_(permeat) is the temperature of thepurified fluid measured by the permeate temperature sensor 303, and cpis the specific heat capacity of water, 4.19 kJ/(kg×K). ΔT is thetemperature difference from tank 350 to after heater 302: T₂-T_(RO).Thus, by controlling, by the control unit 112, any or both of the powerof the heater 302 and the pumping rate of the RO-pump 450, thetemperature of the RO-membrane 324, and thus the water in the tank 350,may be controlled to a certain temperature. In addition, therecirculation in the first fluid path may be stopped upon a certaintemperature of the RO-membrane 324 being achieved, optionally therecirculation may be maintained for a certain time period in order toheat disinfect the RO-membrane 324.

The recirculation of the fluid aims to use the increase of thetemperature of the purified fluid, by returning the heated purifiedfluid to the feed fluid path 391, and eventually to the tank 350. Theenergy of the heated fluid is then transferred to the feed fluid andthereby the heating of the purified fluid is faster. The recirculationalso has the effect that the whole water purification apparatus 300 willbecome warm. The heat loss to the environment/surrounding in the comingheat disinfection can then be reduced, and the coming heat disinfectioncan thus be made faster. According to one embodiment, the inflow to thetank 350 is stopped during the heating, while recirculating the fluid,such that no cold water enters the tank 350. Thereby, the heating may bemade faster.

In response to the first temperature dependent criterion beingfulfilled, the control unit 112 is configured to control the valvearrangement 305 to re-direct the heated purified fluid to flow into thesecond fluid path, for example the second recirculation path 375 and/orthe second drain path 388, of the water purification apparatus 300. Thecontrol unit 112 is further configured to control heating, with theheater 302, of the re-directed heated purified fluid in order to fulfila second temperature dependent disinfection criterion for the secondfluid path. The second temperature dependent disinfection criterioncomprises, for example, to achieve a certain temperature of the heatedpurified fluid in the second fluid path for a certain time period.Alternatively, the second temperature dependent disinfection criterioncomprises to simply direct the heated purified fluid to the second fluidpath for a certain predetermined time period, that is specific for thesecond fluid path or for any component to be heat disinfected that ispart of, or arranged to, the second fluid path. The second fluid pathshould thus be exposed to heated purified fluid at a certain temperaturefor a certain time, in order to heat disinfect the second fluid path.

FIG. 6 illustrates a second exemplary embodiment of a water purificationapparatus 300, with fluid paths marked up for illustrating an example ofa partial disinfection of the fluid path of the water purificationapparatus 300. Further below, a method for cleaning the fluid path ofthe water purification apparatus 300 of FIG. 6 during the partialdisinfection will be explained, with reference to the flowcharts ofFIGS. 8-12.

The differences in line style of the fluid paths of FIG. 6 illustratesthe main flows in a first fluid path (thicker lines) and a second fluidpath (dash double dot line), during the example embodiment of thepartial disinfection.

The second exemplary embodiment is essentially the same as the firstexemplary embodiment, except that it also comprises a conductivitysensor 336, or conductivity cell, in the first drain path 384. Theproduct port 128 and the drain port 118 are closed by the port lid 401.When the port lid 401 is closed, the product port 128 and the drain port118 becomes connected by a path 401 a, such that heated fluid can flowfrom the product port 128 and into the drain port 118 and further to thedrain 339 via the first drain path 384. According to one embodimentshown in FIGS. 5-7, the path 401 a is defined by the port lid 401, andis at least partly included in the port lid 401. According to anotherembodiment shown in FIG. 13, the path 401 a is included in the waterpurification apparatus 300, and is defined by a separate line connectingthe product port 128 and drain port 118. The separate line is notaccessible when the port lid 401 is open. When the port lid 401 isclosed, the port lid 401 opens up the separate line such that heatedfluid may flow from the product port 128 to the drain port 118 via theseparate line, in order to disinfect the product port 128 and the drainport 118.

In an example embodiment, the product port 128 and the drain port 118are in fluid communication with the second fluid path. The secondtemperature dependent disinfection criterion may then comprise to fulfila temperature dependent disinfection criterion for the product port 128and/or the drain port 118, e.g. to fulfill the A0 criterion for theports 118, 128. In some embodiments, the temperature dependentdisinfection criterion comprises a predetermined pressure the heatedpurified fluid should have in order to properly disinfect the productport 128 and/or the drain port 118, i.e. “the ports 118, 128”. Thepredetermined pressure is for example measured with a pressure sensor(e.g. pressure sensor 308 in FIG. 13) arranged in the product fluid path371 c.

In an exemplary embodiment, the second fluid path comprises a drainpath, e.g. the first drain path 384, wherein the second temperaturedependent disinfection criterion comprises to fulfil a temperaturedependent disinfection criterion for the drain path.

In an exemplary embodiment, the temperature should thus be at least 75°C. for a certain predetermined time, in order to fulfil the respectiveA0 value for the ports 118, 128 and the first drain path 384.

In an exemplary embodiment, the control unit 112 is configured to causethe water purification apparatus 300 to perform a polisher-devicedisinfection, e.g. an EDI-device disinfection. The EDI-devicedisinfection comprises to control heating of the purified fluid thatwill flow through the EDI-device 306, and thus through the productchannel 306 a of the EDI-device 306, in order to fulfil a temperaturedependent disinfection criterion for the EDI-device 306. The EDI-devicedisinfection further comprises to control the water purificationapparatus 300 to bypass the EDI-device 306, in response to thetemperature dependent disinfection criterion for the EDI-device 306 isfulfilled. For example, the control unit 112 is configured to execute anEDI-device disinfection program comprising to control the waterpurification apparatus 300 to perform the EDI-device disinfection bymeans of the valve arrangement 305, the heater 302, the firsttemperature sensor and/or the second temperature sensor etc. The valvearrangement 305 includes at least one or several valves of valve devices305 a-305 d. However, the valve arrangement 305 may include more valvesand valve devices as shown in FIG. 13. The heated purified fluid maythen go via a first fluid path or second fluid path including aconcentrate path 377 c connecting a concentrate channel 306 b of theEDI-device 306 with the tank 350.

According to one embodiment, the first fluid path comprises theEDI-device 306. The first fluid path then includes the product channel306 a (FIG. 4) of the EDI-device 306. In one embodiment, the first fluidpath includes all of the channels of the EDI-device 306. Alternatively,the second fluid path comprises the EDI-device 306. The second fluidpath then includes the product channel 306 a (FIG. 4) of the EDI-device306. In one embodiment, the second fluid path includes all the channelsof the EDI-device 306.

In an alternative embodiment, the polisher device comprises a mixed bedfilter device. Thus, in the embodiments herein described with referenceto an EDI-device, the EDI-device is replaced with the mixed bed filterdevice.

After the actual disinfection of the water purification apparatus 300,the control unit 112 is configured to perform one or several postdisinfection programs.

For example, the control unit 112 is configured to cause the waterpurification apparatus 300 to perform an active cool down of anRO-membrane 324 of the RO-device 301. The active cool down comprises to:control the RO-pump 450 to pump water from a water source 398 to theRO-device 301 until a predetermined cooling criterion for the RO,membrane 324 has been fulfilled. The active cool down further comprisesto control the valve arrangement to drain reject fluid from the waterpurification apparatus 300, to the drain 339. The active cool down mayinclude to close the permeate side of the RO-membrane 324, for exampleby closing the valve devices downstream the permeate outlet 301 b.

In another example, the water purification apparatus 300 comprises asecond pump 316 (see FIG. 13). The second pump may also be referred toas a chemical intake pump. The control unit 112 is in this embodimentconfigured to cause the water purification apparatus 300 to control thesecond pump 316 to pump air (i.e. from an air inflow, e.g. in the tank350, backwards through the first recirculation path 381). The controlunit 112 is further configured to control the valve arrangement 305 todirect the air past the closed product port 128 and/or past the closeddrain port 118 of the water purification apparatus 300 in order toremove water from the port(s) 118, 128.

In a further exemplary embodiment, the second pump 316 is arranged to beused for pumping a cleaning agent such as citric acid. The control unit112 is in this embodiment configured to cause the water purificationapparatus 300 to control the second pump 316 to pump a cleaning agentinto the feed fluid path 391, and to circulate the cleaning agent in thefirst reject recirculation path and the second reject recirculationpath, from the reject outlet 301 c to the feed inlet 301 a, in order toremove scaling on an RO-membrane 324 of the RO-device 301.

FIG. 7 illustrates the third exemplary embodiment of a waterpurification apparatus 300, with fluid paths marked up for illustratinganother example of a partial disinfection of the fluid path of the waterpurification apparatus 300. The differences in line style of the fluidpaths illustrates the main flows in the first fluid path (thicker lines)and the second fluid path (dash double dot line), during the partialdisinfection. In the third exemplary embodiment, there is norecirculation of fluid in order to heat the fluid, except for the minorflow from the concentrate channel 306 b of the EDI-device 306 back tothe tank 350 via the concentrate fluid path 377 c (and in some casesalso the minor flow from the electrode channel 306 c). If the polisherdevice alternatively comprises a mixed bed filter device, there is norecirculation of fluid from the bed filter device. In the example ofFIG. 7, the control unit 112 is configured to cause the waterpurification apparatus 300 to control heating, with the heater 302, ofthe purified fluid in the purified fluid path 371, in order to fulfil atemperature dependent disinfection criterion for the EDI-device 306. Inresponse to the temperature dependent disinfection criterion for theEDI-device 306 is fulfilled, the control unit 112 is configured tocontrol the water purification apparatus 300 to re-direct the heatedpurified fluid into a second fluid path, here including the bypass path371 d and the product fluid path 371 c, and thereby to bypass theEDI-device 306. In response to the temperature dependent disinfectioncriterion for the EDI-device 306 being fulfilled, the control unit 112is also configured to control heating, with the heater 302, of thepurified fluid in the second fluid path in order to fulfil a temperaturedependent disinfection criterion for the second fluid path. The heater302 is here configured to heat the purified fluid in one step from about20° C. to above 75° C.

The second fluid path comprises the ports 118, 128, which thus are influid communication with the second fluid path. The second temperaturedependent disinfection criterion comprises to fulfil a temperaturedependent disinfection criterion for the ports 118, 128. Further, thesecond fluid path also comprises the first drain path 384, and thesecond temperature dependent disinfection criterion then comprises tofulfil a temperature dependent disinfection criterion for the firstdrain path 384. Thus, the heated purified fluid is passed via the ports118, 128 and via the first drain path 384 to drain 339. The temperatureis measured in the first drain path 384, with the drain path temperaturesensor 315. The temperature should thus be at least 75° C. for a certainpredetermined time, in order to fulfil the respective A0 value for theports 118, 128 and the first drain path 384. The second temperaturedependent criterion for the port may also include to have a certainpressure of the fluid that flows past the port or ports 118, 128. Thepressure is for example monitored with a pressure sensor 308 (see FIG.13) in the product fluid path 371 c, and controlled by means of theRO-pump 450 and/or the flow control device 305 a.

Methods for Cleaning

In the following, a plurality of different cleaning programs will beexplained, with reference to the flow charts of FIGS. 8-12, to theexemplary embodiments of the water purification apparatuses of FIGS.5-7, and the detailed description of the water purification apparatus ofFIG. 13.

In some embodiments, a cleaning program may start with one or several ofthe following starting programs:

Flushing of the RO-Membrane Reject Side, S1 a

Flushing the RO-membrane reject side is performed to lower theconcentrations of substances present after a treatment. As anexplanation, when sending reject fluid back to the feed side of theRO-membrane 324, the reject fluid will get more and more concentrated upto a point where feed fluid, reject fluid and the amount of permeatefluid produced are in balance.

Flushing of the First Drain Path, S1 b

Flushing the first drain path 384 is performed to remove as much of theresiduals from the patient fluid that may be present. It is important todo this flush with cold water in order to get a best possible flush. Ifsending heated fluid directly, proteins may denaturate on the fluid pathsurfaces, thereby making them much harder to clean.

Cleaning First Drain Path with Cleaning Agent, S1 c

In this program, a cleaning agent such as citric acid is distributedwith the second pump 316, via a chemical intake path 382 (FIG. 13), tothe first drain path 384, i.e. the patient drain path, including thepatient conductivity sensor 336, at the same time as the first drainpath 384 is flushed with cold water. To detect that the cleaning agentis taken in the conductivity sensor 336 is used. Both parallel paths384, 384 a should be filled with cleaning agent (FIG. 13). The drainline valve 341 is first open and the primary drain line valve 338 isclosed. That enables the use of conductivity sensor 336 to detect whenthe cleaning agent has reached the drain 339. After filling withcleaning agent, the product water valve 305 d is closed and all producedfluid is directed back to the tank 350. In one embodiment, the cleaningagent is active during the heating phase and disinfection phase of thepurified fluid path 371 and will according to one embodiment not beflushed away until the port disinfection starts. The citric acid willact as an anti-scaling agent and also remove any residues left after thecold water flush. The citric acid will also have a disinfection effect,due to the low pH of the citric acid. The fluid present in the firstdrain path 384 stays there for performing its descaling and cleaningactivity while the water purification apparatus 300 prepares for theheating disinfection phase.

When the optional starting programs are finished, the water purificationapparatus 300 thus starts to prepare itself for heat disinfection:

In some embodiments, the preparations comprise controlling S2 the fluidlevel in the tank 350 to a predetermined level of the tank 350, beforeheating of the purified fluid starts. For example, the fluid level iscontrolled to an appropriate level such that, when the fluid in the tank350 is heated, there is room for the fluid to expand without leaking oute.g. via tank air vent line 325. According to one embodiment, the inletvalve 332 and/or the tank valve 328 are closed when the predeterminedlevel has been reached (see FIG. 13). Thereby no fresh cold water isintroduced during the heating, e.g. during the recirculation for heatingthe fluid, and the fluid may be heated faster. The three-way valve 305 bis set to direct all water back to the tank 350. Optionally, a rejectbypass valve 321 is opened to bypass the restrictors of constant flowdevice 318, in order to reduce the pressure over the RO-membrane 324(see FIG. 13).

After the optional preparations have been made, a method for cleaningthe water purification apparatus 300 can be started. In the following, aplurality of different cleaning methods will be explained. In someembodiments, only heat disinfection is performed for cleaning theapparatus 300. Only one pump, thus the RO pump 450, is used to produce aflow for heat disinfecting the fluid paths of the apparatus 300 (exceptin embodiments when also the pump 316 is actuated to heat disinfect thefluid path the pump 316 is arranged to).

Complete Heat Disinfection

Methods for performing a complete disinfection will now be explainedwith reference to the flowcharts of FIGS. 8-12, and to the FIG. 5.

Many parts of the water purification apparatus 300 belong, as explainedabove, to the feed side of the water purification apparatus 300 (to thefeed side of the RO-device 301) and fluid paths leading to this side.Thus, complete heat disinfection includes disinfecting those parts, andis done some days apart, typically twice a week. In one exemplaryembodiment, the product channel 306 a of the EDI-device 306 (FIG. 5) isalways omitted, i.e. bypassed, during the complete heat disinfection.The reason is to protect the EDI-device 306 from metals that may passthe RO-membrane 324 while the RO-membrane 324 is heated up since theRO-membrane 324 gets more permeable as the temperature increases. Theseparts are taken care of during other disinfection phases, i.e. the portsand drain phase disinfection, as will be explained in the following.Further, if the polisher-device comprises a mixed bed filter device, themixed bed filter device is always bypassed during the complete heatdisinfection.

In the following two different complete disinfection programs will beexplained: a Regular program and a Planned absence program.

1a. Regular Program

The regular program runs according to what is recommended by theRO-membrane manufacturer, i.e. not increasing the temperature more perunit time than recommended. Also, when lowering the temperature, thedecrease needs to be less, per unit time, than a maximum defined by themanufacturer. The latter is included in active cool down. Specifically,the heating and cool down procedures are important for temperaturesoutside the normal operation range of the membrane, e.g. above 40° C.The active cool down will also reduce the time at high temperature forthe RO-membrane, which will increase the lifetime of the RO-membrane.

The regular heat disinfection will now be explained. Steps done for riskmitigation, such as e.g. comparing flow sensors, testing that the fluidpath does not leak, and so on, are here omitted for brevity, but couldbe included in the program.

Disinfection Starts—First Sequence

Before the program is started, the RO-pump 450 needs to be started suchthat fluid is pumped through the RO-membrane 324 via the heater 302. Themethod then comprises controlling S3 the heating of the purified fluid.For example, when the flow sensor 410 detects a flow, the heater 302 isswitched on. Reference is now made to FIG. 5, where the first fluid pathis indicated by the thick line from the permeate outlet 301 b to tank350 and further to the feed inlet 301 a. The three-way valve 305 c iscontrolled to direct the heated permeate fluid into the bypass path 371d. The three-way valve 305 c is thus set to bypass the EDI-device 306.As will be further described below in relation to FIG. 13, the heatedfluid is directed to the air trap chamber 319 and back to the tank 350via the emptying valve 396.

The heater 302 is then set to deliver power in such amount that thetemperature of the RO-membrane 324 does not increase faster than apredetermined rate, i.e. a predetermined number of degrees per unittime, e.g. 3° C./min, in order to not stress the RO-membrane 324. Thepredetermined rate is for example set by the supplier of the RO-membrane324.

The method further comprises re-circulating S4 the heated purified fluidin the first fluid path until a first temperature dependent criterion isfulfilled S4 d. For example, the method comprises measuring S4 b thetemperature of the purified fluid in the first fluid path, and/ormeasuring S4 c a flow rate the purified fluid. The first temperaturedependent criterion comprises, for example, controlling heating, basedon the measured temperature, of the purified fluid such that atemperature of the purified fluid is within a range of 70°-95° Celsius.The temperature is in some embodiment set to be sufficient fordisinfection of the first fluid path, or a component in the first fluidpath. In other words, the first temperature dependent criterioncomprises re-circulating the heated purified fluid in the first fluidpath to the feed fluid path, until a first temperature dependentdisinfection criterion is fulfilled. The temperature of the purifiedfluid may then be measured with the product fluid temperature sensor313, and the temperature should reach a predetermined temperaturesufficient for disinfection, e.g. 85° C.

In some other embodiments, the temperature of the purified fluid shouldreach a certain temperature, which corresponds to that the fluid in thetank 350 (and thus the RO-membrane 324) is pre-heated to a certainlevel, e.g. 40° C. The heating is also depending on the flow rate of thepurified fluid. Thus, in some embodiment, the first temperaturedependent criterion comprises to control heating and pumping with theRO-pump 450, based on the measured temperature and the measured flowrate in the permeate fluid path 371 a, such that the purified fluidobtains a predetermined temperature dependent flow rate.

In another embodiment, the first temperature dependent criterioncomprises to heat the RO-membrane 324 to a certain temperature for acertain time, e.g. such that an A0-criterion for the RO-membrane 324 isachieved. For example, the A0-criterion may include that the certaintemperature is between 70-85° C., and the certain time is between 5 to20 minutes. The A0-concept will be explained in more detail in thefollowing.

If the first criterion S4 d is not fulfilled, the control of the heatingS3 and the re-circulating S4 is continued.

Disinfection Continues—Second Sequence

In response to the first temperature dependent criterion beingfulfilled, the method comprises re-directing S5 the heated purifiedfluid to flow in a second fluid path of the water purification apparatus300. The second fluid path may encompass one, several or all of thepaths on the permeate side of the water purification apparatus 300.However, according to one embodiment, the product channel 306 a of theEDI-device 306 may constantly be bypassed during a completedisinfection.

The method further comprises to control heating S6 of the redirectedheated purified fluid, in order to fulfil a second temperature dependentdisinfection criterion for the second fluid path. All paths need toreach a prescribed disinfection criterion, specific for that path orcomponent in the path. The disinfection criterion includes, in someembodiments, to reach an A0-value that will be described in thefollowing. This can be achieved by either continuously measuring thetemperature at strategic points such as with the product fluidtemperature sensor 313 and/or with a drain path temperature sensor 315and calculate the A0-values, or use validated sequences to achieve thecorrect A0-values. In other words, the method comprises measuring S61 athe temperature of the fluid in the second fluid path. In someembodiments, the method comprises determining, based on the measuredtemperature, a time duration for heat disinfecting the second fluid pathwith the fluid at the measured temperature, such that a bacterialreduction criterion is fulfilled, and controlling heat disinfection ofthe second fluid path based on the time duration. The second temperaturedependent criterion then comprises to heat disinfect the second fluidpath during the time duration. The time duration is for examplecalculated by using the A0-concept. Thereby, the required disinfectionof the second fluid path, or a component of the second fluid path, canbe achieved.

If the A0-values are calculated during the disinfection there is apossibility to minimize the energy consumption and time used for thedisinfection program compared to a method which use validated sequences.

The method checks, for each second path, if the second criterion isfulfilled S61 b. If not, the method continues to control heating S6 ofthe fluid in the second fluid path. If the second criterion is fulfilledfor one second path, the method checks S61 c if there are more secondfluid paths to be disinfected. If so, the method re-directs S5 to theother second fluid path that is not yet disinfected, and controlsheating S6 of the fluid in the second fluid path.

The disinfection is finished when the second criterion is fulfilled S61b for all paths on the permeate side. For example, if all prescribedA0-values for the second fluid paths have been met, the disinfection isfinished.

In some embodiments, the method continues, after the disinfection isfinished, to perform one or several post disinfection programs, e.g. anactive cool down program and an emptying of ports of water program.

Active Cool Down Including Disinfection of Ports and Drain Path

During the active cool down S7, illustrated in the flow chart of FIG.11, inlet valve 332 and/or the tank valve 328 are opened to let coldwater into the apparatus 300 again, and the three-way valve 305 b isopened to drain 339 to let hot water to drain 339.

At the same time a partial disinfection program may be performed, inorder to disinfect the ports 118, 128 and the first drain path 384,while bypassing the EDI-device 306. Also parts leading to the ports 118,128 and the first drain path 384 are heat disinfected during the partialdisinfection, such as product water valve 305 d and the fluid path fromthe air trap chamber 319 to the product port 128 (see FIG. 13). Duringthe partial disinfection program, heated purified fluid, e.g. 85° C. orabove, is passed past the ports 118, 128 and further down through thefirst drain path 384 in order to disinfect the two paths 384, 384 aherein (see FIG. 13). The level of disinfection is secured by the drainpath temperature sensor 315. When sufficient disinfection of the ports118, 128 and the first drain path 384 has been achieved the permeateside of the RO-membrane 324 is closed S64 and left to be cooled down.For further explanation, reference is made to the detailed descriptionof partial disinfection further down, which embodiments also may be madein the complete disinfection programs.

The cool down of the RO-membrane 324 continues until an estimatedtemperature of below e.g. 40° C. on the reject side of the RO-membrane324 has been reached. The estimation of the temperature is first basedon the permeate flow temperature measured by permeate temperature sensor303 and the energy needed to reach the temperature during the heating ofthe first drain path 384. By also knowing the amount of heated watersent to the second drain path 388 and what the temperature of the feedwater measured by feed water temperature sensor 326 is, it is possibleto estimate when the reject side temperature has become below 40° C. Inother words, the active cool down comprises to pump S71 water from awater source to the RO-device 301 until a predetermined coolingcriterion S72 for the RO-membrane 324 has been fulfilled, and to controldraining S73 of reject fluid from the water purification apparatus 300.

After the active cool down program has been finished, an optionalprogram for emptying the ports of water can be performed.

Emptying of Ports of Water (Optional)

Directly after having disinfected the ports and the first drain path384, in parallel with the active cool down, the second pump 316 isstarted to pump air S8 (FIG. 10) in from the tank 350 (the surfaces ofthe tank 350 are still hot) and pumps it past the ports 118, 128 toremove any water from them. This step may be omitted for improvedbacteriological status between treatments. However, the ports 118, 128should then be emptied at the beginning of the start-up of the nexttreatment, before the patient is asked to attach the disposable line set40.

After having finished the active cool down program, and optionally theemptying of ports and water program, the water purification apparatus300 is for example set in a low power mode, e.g. to standby mode, or isshut down. The water purification apparatus 300 may also be configuredto send a cleaning update S10 to the cycler 20.

1b. Planned Absence Program

The planned absence program is basically the same as the regularprogram. What differs are three phases:

-   -   1. The cool down program is not done. The water purification        apparatus 1 is left for passive cool down to minimize the risk        of bacteria's entering the fluid path. However, the partial        disinfection including ports and drain path disinfection is        done.    -   2. Emptying of the ports program is not done, for the same        reason as for No. 1 above.    -   3. Chemical cleaning program for RO-membrane        -   A small amount of a cleaning agent, corresponding to 0.3-1%            of cleaning agent (e.g. 0.3-1% citric acid) in the reject            paths 385 b, 389, is introduced into the fluid path of the            apparatus 300 by using the second pump 316. The permeate            fluid is now heated using full power to the heater 302 into            a heated purified fluid. Into this stream of heated purified            fluid, the second pump 316 is pumping a small amount of            cleaning agent, for example an amount of citric acid, e.g.            15 ml citric acid. When the cleaning agent has been            transported to the tank 350 the permeate flow is stopped.            The fluid in the tank 350 is now recirculated for a            predetermined time in the feed/reject side loop while            three-way valve 305 b is closed to drain 339, so that the            cleaning agent reaches all parts of the reject side and            mainly the RO-membrane 324. In other words, the program            includes circulating a cleaning agent S9 such as citric acid            in a reject recirculation path from a reject outlet to the            feed inlet of the RO-device, in order to remove scaling on            an RO-membrane of the RO-device. During the recirculation,            no fluid is passed through the RO-membrane 324 to the            permeate side. The chemical cleaning program results in a            descaling of the RO-membrane 324 in order to prevent            buildups of scale on the RO-membrane 324 to, as far as            possible, keep the performance of the RO-device 301 constant            over time. The reason for not doing it is to minimize            possible intake of bacteria. The cleaning agent may be left            in the fluid path of the water purification apparatus 300            until next treatment is started.

The planned absence program is done prior to a planned pause in the useof the water purification apparatus 300, e.g. when the patient plans tobe away from home for several days. Once the prescribed disinfectioncriterion has been met, e.g. a predetermined time at a temperature abovea predefined temperature, the water purification apparatus 300 is set ine.g. a low power mode such as standby. By doing so, no living organismsshould be present in the fluid path hence prolonging the time to when anew disinfection needs to be performed.

In one example embodiment, a complete cleaning of the water purificationapparatus 300 comprises performing, in the specific order from a) to d):

a) Running a chemical cleaning program for descaling, and to some extentchemical disinfection, of the first drain path 384, including thepatient conductivity sensor 336, with a cleaning agent such as citricacid;b) Heat disinfecting the RO-membrane reject side, including the firstrecirculation path 381 and the second recirculation path 375(essentially all fluid paths of the RO module and the post-treatmentmodule except the first drain path 384, the last part of the productpath and the EDI product channel 306 a and the concentrate channel 306b).c) Heat disinfection of the ports 118, 128 and the first drain path 384;d) Running a chemical cleaning program including descaling of theRO-membrane 324 with a cleaning agent such as citric acid.

2. Partial Heat Disinfection Program

The partial heat disinfection program comprises disinfection of one orseveral of the EDI-device 306, the ports 118, 128, the drain paths 384,388 and the parts leading to the ports 118, 128 and the first drain path384, such as product water valve 305 d and the fluid path from the airtrap chamber 319 to the product port 128 (see FIG. 13). The partial heatdisinfection program may also be referred to as a port and/or drain pathdisinfection program. In some embodiments, a partial heat disinfectionprogram is done after every treatment, unless complete heat disinfectionis done.

A plurality of different partial heat disinfection programs is possible,and in the following some alternatives will be explained.

As the complete programs, each partial heat disinfection program maystart with flushing S1 a the RO-membrane reject side and flushing Sibthe first drain path 384 with cold water, to remove any substancespresent after a treatment.

Thereafter, some alternative partial heat disinfection programs areavailable:

Alternative 1

In this disinfection, the EDI product channel 306 a and the concentratechannel 306 b are included in the fluid path that is heat disinfected.This partial heat disinfection program is preferably run at the samefrequency as the regular heat disinfection but at a different day. Themain steps of this disinfection will be explained in the following.Steps done for risk mitigation, such as e.g. comparing flow sensors,testing that the fluid path does not leak, and so on are omitted.

As an optional pre-step, the water level in the tank 350 is controlledS2 by the water purification apparatus 300 to a predetermined level,e.g. up to its top level.

A plurality of different options for heating the EDI product waterchannel 306 is available:

Alternative 1—First Option

In a first sequence, feed water is pumped by the RO-pump 450 through theRO-device 301, and heating of the purified fluid is controlled S3 bycontrolling the power of the heater 302. The heated purified fluid isre-circulated S4 in a first fluid path including the first recirculationpath 381 but with the EDI-device 306 bypassed via the bypass path 371 d,as illustrated in FIG. 6 with a thick line. With reference to FIG. 13,the first fluid path comprises the permeate fluid path 371 a, thepolisher fluid path 371 b, the product fluid path 371 c up to the airtrap chamber 319, and the first recirculation path 381 back to the tank350 via the emptying valve 396. The method may include to controlheating S3 and re-circulating S4 based by measuring S4 b the temperatureof the purified fluid in the first fluid path. The heating S3 andre-circulating S4 is then continued until a first temperature dependentcriterion has been fulfilled. In one embodiment, the first temperaturedependent criterion comprises controlling heating, based on the measuredtemperature, of the purified fluid, such that a temperature of thepurified fluid is within a range of 70-95° Celsius. In some embodiment,this corresponds to that the fluid in the tank 350 and thus theRO-membrane 324 has been heated to approximately 40° C. Alternatively,the first temperature dependent criterion comprises to control heatingof the purified fluid, and pumping with the RO-pump 450, based on themeasured temperature and the measured flow rate of the purified fluid,such that the purified fluid obtains a predetermined temperaturedependent flow rate. For example, the method comprises measuring S4 bthe temperature of the purified fluid in the first fluid path, and/ormeasuring S4 c a flow rate of the purified fluid.

In a second sequence, when the water in the tank 350 add consequentlyalso the ROU-membrane 324 have been heated to approximately 40° C. andthus fulfil a first temperature dependent criterion, the heated purifiedfluid is re-directed S5 to flow in a second fluid path, as indicated inFIG. 6 with the dash double dot line. The first temperature dependentcriterion for example comprises controlling heating, based on themeasured temperature, of the purified fluid such that a temperature ofthe purified fluid is within a range of 70-95° C. The heated purifiedfluid is then further heated S62 a in order to fulfil a temperaturedependent disinfection criterion of the EDI-device 306. When thetemperature dependent disinfection criterion for the EDI-device 301 hasbeen fulfilled S62 c, which is e.g. determined by measuring S62 b thetemperature of the heated fluid passed in the product channel 306 a, themethod returns to step S5. The heated fluid is now re-directed to bypassthe EDI-device 306, and thus into another second fluid path, that is thesame as the previously mentioned second fluid path, except that theEDI-device 306 is now bypassed. The purified fluid is now continuouslyre-directed S5 to flow into the other second fluid path, and heated S6,until a second criterion for the second fluid path is fulfilled S61 b.The second criterion for example comprises to fulfil the temperaturedependent disinfection criterion for the port(s) 118, 128 and/or tofulfil a temperature dependent disinfection criterion for the firstdrain path 384. The method includes according to some embodiment,alternating the flow in the first drain path 384 between theconductivity drain path with the conductivity sensor 336 and the bypasspath 384 a. Any of the temperature disinfection criterions may includefulfilling a predetermined A0-criterion, e.g. an A0-value, for theEDI-device 306, for the port(s) 118, 128 or for the first drain path384, respectively. In order to fulfil the A0-criterion, the temperaturehas to be measured. In other words, the method may comprise measuringS61 a the temperature of the fluid in the second fluid path.

In some embodiments, the second temperature dependent criterioncomprises determining, based on the measured temperature, a timeduration for heat disinfecting the second fluid path with the fluid atthe measured temperature, such that a bacterial reduction criterion isfulfilled, and controlling heat disinfection of the second fluid pathbased on the time duration. The time duration is for example anA0-value, expressed as a time duration Δt. Thereby, the requireddisinfection of the second fluid path, or a component of the secondfluid path, can be achieved. If the temperature of the tank 350, i.e.the RO-membrane 324, becomes too low to achieve any of the disinfectioncriteria, the method returns to step S3 in order to heat the water inthe tank 350 again.

Alternative 1—Second Option

The second option also includes a first sequence and a second sequence.

In the first sequence feed water is pumped by the RO-pump 450 throughthe RO-device 301, and heating of the purified fluid, by the heater 302,is controlled S3. The heated purified fluid is recirculated S4 in afirst fluid path, including the second recirculation path 375 nowincluding the EDI-device 306, as illustrated in FIG. 6 with a thickline. As will be further shown below with reference to FIG. 13, thefirst fluid path comprises the permeate fluid path 371 a, the polisherfluid path 371 b including the product channel 306 a and the concentratechannel 306 b, and the second recirculation path 375 back to the tank350. The purified heated fluid is now passed from the reverse side ofthe product channel 306 a of the EDI-device 306 back to the tank 350.Alternatively, the heated fluid is first recirculated in the firstrecirculation path 381 in order to heat the fluid to a predeterminedtemperature, e.g. 85° C., measured with the product fluid temperaturesensor 313, corresponding to a temperature of the RO-membrane 324 of 40°C., before the heated fluid is passed through the EDI-device 306. Themethod then further comprises controlling heating S4 a of the heatedpurified fluid that will flow through the EDI-device 306. Thetemperature is measured using the permeate temperature sensor 303. Whenthe permeate temperature sensor 303 measures 35° C., the heater 302 ispowered to heat the permeate fluid rapidly to between 70-85° C., inorder to get a flow of as high temperature water through the productchannel 306 a of the EDI-device 306 as possible. Optionally, at the sametime as the heater 302 is powered to heat rapidly, the reject side pathsare opened maximally such that the recirculated reject fluid is mixedwith recirculated heated purified fluid, while sending as much of thereject fluid as possible to drain 339, to thereby avoid that theRO-membrane 324 is heated above its temperature limit.

According to one embodiment, the EDI-device 306 is powered during heatdisinfection thereof, in order to minimize decay of capacity of theEDI-device 306, and to minimize the time needed for subsequent recoveryof capacity of the EDI-device 306 caused by the decay of capacity.

If the temperature of the fresh incoming water is as high as 35° C.already from the start, then the heating may need to be temporarilyinterrupted while lowering the temperature of the feed/reject sidewater. According to one embodiment, this is done by shutting off theheater 302 completely, while continuing to pump the mixed return andfresh water in the tank 350 to the reject side drain and recirculatingthe permeate water back to the tank 350 via a maximally open flowcontrol device 305 a. When the temperature measured by the permeatetemperature sensor 303 has been lowered sufficiently (to not wait toolong and getting too low temperature inside of the EDI product channel306 a) the heating of the EDI product channel 306 a is restarted. Theprocedure may then need to be repeated one or more times. When thedisinfection criterion for the EDI-device 306, e.g. the appropriateA0-value for the EDI-device, has been achieved, determined by means ofmeasurements by the permeate temperature sensor 303, heating stops andthe EDI product channel 306 a is closed, i.e. by closing the valvedevice 307 (see FIG. 13). The EDI-device 306 is thereby bypassed. Theheated purified fluid is now instead recirculated back to the tank 305by opening the emptying valve 396, i.e. through the first recirculationpath 381. The temperature of the heated purified fluid in the firstrecirculation path is controlled to have a temperature of 40° C., whichis measured by the product fluid temperature sensor 313. In other words,the first criterion may comprise that: the disinfection criterion forthe EDI-device 306 is fulfilled, the EDI-device 306 is bypassed, theheated purified fluid is recirculated through the first recirculationpath 381 and the temperature is controlled to approximately 40° C.

In the second sequence, when the first criterion has been fulfilled, andthus the temperature of the heated purified fluid has reached apredetermined temperature of 40° C., the heated fluid is re-directed S5to flow into a second fluid path including the ports 118, 128 and thefirst drain path 384, while heating S6 the purified fluid. The secondpredetermined criterion comprises to heat the purified fluid to apredetermined temperature to 85°, and then to direct the heated purifiedfluid to the different paths of the first drain path 384 in analternating sequence, for example 1 minute in one path followed by 1minute in the other path, until the entire first drain path 384 hasreached the required A0-value. If the purified fluid cannot be heated toabove 85°, e.g. in case the incoming water is so cold that the heater302 cannot heat the purified fluid to above 75° C., measured with theproduct fluid temperature sensor 313, then the heated purified fluid issent back to the tank 350 and the water purification apparatus 300 againcontrols the heater 302 to reach a temperature of 40° C. in the firstsequence. As soon as this is achieved the heater 302 is again set toreach a temperature above 85° C. with the product fluid temperaturesensor 313 and start sending the heated purified fluid past the port118, 128 and to drain 339 in the second sequence. The temperature in thefirst drain path 384 is monitored by the drain path temperature sensor315 such that the temperature in the first drain path 384 does not gobelow 65° C. (plus some margin). If so, a prolonged disinfection time isrequired for disinfecting the first drain path 384.

When the respective disinfection criterion has been fulfilled, the heatdisinfection of the respective parts of the fluid path of the waterpurification apparatus 300 is considered finished.

In some embodiments, the heat disinfection is followed by a chemicalcleaning program for the RO-membrane 324, as follows:

When the required disinfection has been reached, that is the respectivedisinfection criterions have been fulfilled, the three-way valve 317 isclosed and the permeate flow is looped back to the tank 350 via the airtrap chamber 319 and back to the tank 350 via the emptying valve 396.The permeate fluid is now heated, e.g. using full power to the heater302, to obtain a heated purified fluid. The second pump 316 is pumping asmall amount of cleaning agent into this stream of heated purifiedfluid. The small amount of cleaning agent is for example an amount ofcitric acid, e.g. 15 ml, for chemically cleaning the RO-membrane 324, ashas previously explained in connection with the planned absence program.

An active cool down program to cool down the RO-membrane 324, as hasbeen previously explained, may be performed simultaneously as any of thepartial heat disinfection programs are performed.

After the heat disinfection, and optionally also the chemical cleaningprogram, is finished, the emptying the port(s) of water program may berun. After having finished the active cool down program, and optionallyalso the emptying the port(s) of water program, the water purificationapparatus 300 is shut down.

Alternative 2

This alternative 2 is the same as alternative 1, except that the EDIproduct channel 306 a is not included and thus not disinfected. Thus,the steps in alternative 1 describing how the product water channel 306is heat disinfected are omitted in alternative 2. This partial heatdisinfection program is preferably run after each use of the waterpurification apparatus.

Alternative 3

This alternative 3 is the same as alternative 2, but additionallyincludes the starting program Sic, explained in connection with thecomplete program, to use a cleaning agent before heating starts, toremove/avoid build ups of possible “deposits” (protein, calcium . . . )in the first drain path 384, before the partial heat disinfectionstarts. It should be run as often as is needed to make sure the firstdrain path 384 is clean, thereby minimizing the risk of an alteredconductivity cell (CP) constant of the conductivity sensor 336.

Alternative 4

An alternative partial disinfection method is illustrated in FIG. 7 andin the flowchart of FIG. 12. The method may start with the same steps S1and S2 as have been previously explained. The method comprises, in afirst sequence, controlling eating S1 a of the purified fluid producedby the RO-device 301, and directing S4 e the heated purified fluid in afirst fluid path, through a product channel of an electrodeionizationunit, EDI-device, wherein the EDI-device also comprises a concentratechannel 306 b. The temperature of the purified fluid is for examplemeasured S4 f by permeate temperature sensor 303 or product fluidtemperature sensor 313. The first fluid path is in FIG. 7 illustratedwith a thicker line.

In response to a temperature dependent disinfection criterion for theEDI-device being fulfilled S4 g, a second sequence starts. The secondsequence comprises re-directing S5 a the heated purified fluid into asecond fluid path to bypass the EDI-device 306 and to control S6 aheating of the re-directed purified fluid, in order to fulfil atemperature dependent disinfection criterion for the second fluid path.The second fluid path is in FIG. 7 illustrated with the dash double dotline. The second temperature dependent disinfection criterion comprises,for example, to fulfil a temperature dependent disinfection criterionfor the port(s) 118, 128 in the second fluid path. Alternatively oradditionally, the second temperature dependent disinfection criterioncomprises to fulfil a temperature dependent disinfection criterion forthe first path.

The method thereafter checks if there are more fluid paths to clean S6b. If there are more fluid paths to clean, then the method returns to S5a. If there are no more fluid paths to clean, the method may perform anyof the steps illustrated in the flowchart of FIG. 10.

The methods have been explained with reference to having an EDI-device.However, as an alternative, the EDI-device is in the above describedmethods replaced with a mixed bed filter device. The criteria describedwith reference to the EDI-device are then exchanged with criteria for amixed bed filter device.

Extended Use of Disposable Line Set

In an alternative embodiment, a method for providing extended life ofdisposable line set 40 is proposed. Here, the disposable line set 40 isused with cycler 20 for more than one treatment. Instead of removing thedisposable line set 40, a cleaning agent such as an agent inhibitingmicrobiological growth is pumped from container 392 and diluted in waterpurification apparatus 300. The diluted agent is pumped into thedisposable line set 40 including cassette 42, its line portions andcontainer 62 connected to the cassette 42. The agent, may in oneembodiment be or include citric acid, or a deviation thereof, and may bepumped from container 392 and diluted in a portion of the fluid path ofwater purification apparatus 300 and then pushed into the circuit ofdisposable line set 40, for example via water line 64 (64 a, 64 b). Inan alternative embodiment, the patient line 50 may be connected to aport of water purification apparatus 300 to receive the diluted agent toprotect the circuit of disposable set 40. Further, alternatively,container 392 may be in direct fluid communication with the cycler 20,for example, via a connection to the patient line 50. Control unit 22causes citric acid (or other suitable acid with or without additives) tobe withdrawn from the container 392 and be directed inside cassette 42,lines connected thereto and container 62.

Control unit 22 is in one embodiment programmed to perform one or moremixing step, so that the agent inhibiting microbiological growth isdiluted with the fluid already contained in the fluid line set 40, whichmay be sterilized product water using the above process to enable thecircuit of disposable set 40 to be used for more than one treatmentinstead of being disposed after a one single use.

In one embodiment, diluted agent is left in the semi-disposable circuit(e.g., circuit of disposable set 40) until a start of preparation for anext treatment. Here, control unit 22 performs a rinsing step to removethe diluted agent from the semi-disposable circuit; the rinsing may bedone with sterilized product water from water purification apparatus300.

It should be appreciated that the above-described procedure is not adisinfection procedure; rather, the procedure with citric acid act as abacteriostatic solution and avoid growth in-between treatments to enableextended use of cassette 42, associated lines and container 62. Itshould also be appreciated that if traces of the citric acid remain inthe circuit of disposable set 40, the minor amount would not harm thepatient considering that a citric acid cycler is a common and safecellular metabolism.

Hot Water Disinfection of Semi-Disposable Line Set

In an alternative multiple use of disposable line set 40 embodiment, theanti-growth inhibiting agent just described is replaced by hot waterdisinfection. Before the disposable line set 40 is heat disinfected, thedisposable line set 40 may be flushed with cold water, i.e. productwater produced with the water purification apparatus 300 without heatingthe water, in order to move away any residuals from the previoustreatment. Thereafter, the heater 302 of water purification apparatus300, under control of control unit 112, heat its water to 70° C. forexample to heat disinfect the fluid path of the water purificationapparatus 300. As illustrated herein, water purification apparatus 300is connected to disposable line set 40 via water line segment 64 ahaving sterilizing grade filters 70 a and 70 b. Sterilizing gradefilters 70 a and 70 b include endotoxin removal capacity to help producesterilized product water. The sterilized product water is used to dilutethe concentrates to prepare ready to use dialysis fluid. The capacity ofdisposable filters 70 a and 70 b depends upon the bioburden of the watersupplied by water purification apparatus 300. Pumping heated waterthrough sterilizing grade filters 70 a and 70 b therefore disinfects thefilters, placing them in better shape for performing multiple treatmentsusing the same disposable set 40. Pumping heated water throughdisposable set 40 also disinfects the disposable set, placing it inbetter shape for multiple treatments. In one embodiment, the heatedfluid used for cleaning the disposable line set 40 includes the cleaningagent. Thereby a combined effect of heat disinfection and cleaning withthe cleaning agent may be achieved.

The A0 Concept

The heat disinfection programs are in some embodiments based onfollowing principle. Heating aims at preventing growth of bacteria (andthus biofilm) on the internal surfaces of the water purificationapparatus fluid path. In order to achieve a sufficient reduction oforganisms a concept herein referred to as the “A0 concept” is used. Theconcept is defined as:

A ₀=Σ10^((T-80)/z) ·Δt  Equation (2)

where z is a value defined by the type of microorganisms that need to bekilled. For bacterial spores, which are the most resistant of allmicroorganisms, a z-value of z=10° C. is considered needed. At atemperature T of 80° C. the A0 expresses the time, Δt in seconds, neededto reach an expected effect. If T=90° C. only a tenth of the time isneeded, i.e. 6 seconds to get an A0 of 60. If T is instead 70° C. thetime needed is tenfold.

In a setting where more than one patient is subjected to the sameinstrument or device it is recommended to achieve an A0-value of morethan 3000*. This is thus the minimal value needed when performing areconditioning of the water purification apparatus 300 when being movedfrom one patient to the next.

During periods when the water device is being used by only one patientan A0-value of 600* should be sufficient. The point of the fluid paththat reaches the lowest temperature is the one for which the A0 shouldbe determined.

The effectiveness of the disinfection is measured by calculation of A0.All temperatures above 65° C. are considered having “disinfectioneffect”. This means that every instance of temperatures above 65° C.,i.e. during heat up and cool down, should be included in the calculationof A0. Therefore, the expression above could alternatively be writtenas:

$\begin{matrix}{A_{0} = {\int_{\overset{\sim}{t} \in {t{({T > {65{\lbrack{{^\circ}\; {C.}}\rbrack}}})}}}{{10^{{({{T{(\overset{\sim}{t})}} - 80})}/z} \cdot d}\overset{\sim}{t}}}} & {{Equation}\mspace{14mu} (3)}\end{matrix}$

meaning that all time, thus every time point, for which the temperatureis above 65° C. are accounted for. Thus, any of the criteria referred toherein, may include an A0-criterion according to the A0-concept.

*Numbers are found in an article “Thermal Disinfection—The A0 Conceptand the Biological Background” by Urs Rosenberg, volume 11, 2003.References are in this article done to prEN14476 and prEN15883.

Detailed Description of a Water Purification Apparatus

FIG. 13 illustrates an example embodiment of the water purificationapparatus 300. In other embodiments, the water purification apparatus300 may include less or more components or modules. The waterpurification apparatus 300 of FIG. 13 receives water from a water source398 (FIG. 3), such as a continuous source of potable or drinkable waterfrom a patient's home. In various embodiments, water purificationapparatus 300 may be installed in a room having access to the watersource 398 to provide WFPD to cycler 20 as discussed herein. The wateris optionally filtered using a particle pre-filter 334 to remove dirtand sediment, before it is delivered to the water purification apparatus300. The water enters the water purification apparatus 300 via the waterinlet port 333. As previously described, the water purificationapparatus 300 includes a pre-treatment module 160, a RO module 170 and apost-treatment module 180. The pre-treatment module 160 includes aparticle filter and an activated carbon filter, i.e. an activated carbonbed, to further remove contaminants and impurities. The particle filterand the activated carbon filter are embodied in one single filterpackage 331. The single package 331 is a disposable package. Thepre-treatment module 160 includes an inlet valve 332 and a constant flowdevice 330 upstream the filter package 331. The inlet valve 332 controlsthe feed water inflow by control of the control unit 112. The constantflow device 330 provides a constant flow to the tank 350 providing thatthe water pressure is above a minimum pressure for constant flow device330. Further, pre-treatment module 160 comprises a sampling valve 329with a sampling port outlet 329 a, a tank valve 328, a pre-treatmentconductivity sensor 327 and a feed water temperature sensor 326downstream the filter package 331. The sampling port outlet 329 a allowsa sample to be taken from the feed water, e.g. to test the chlorinelevel. The tank valve 328 controls the flow of filtered feed water tothe tank 350. The pre-treatment conductivity sensor 327 monitors theconductivity of the filtered feed water, and the feed water temperaturesensor 326 monitors the temperature of the filtered feed water. Thetemperature of the filtered feed water is for example needed tocalibrate the conductivity measurement of the filtered feed water. Thedescribed components are included in a pre-treatment fluid path 390. Thepre-treatment fluid path 390 is connected to the water inlet port 333and ends into the tank 350. The inlet valve 332 and the tank valve 328are configured to be controlled by the control unit 112 of the waterpurification apparatus 300. Water softening in the pre-treatment module160 may alternatively or additionally be achieved using lime softening,ion-exchange resins or an anti-scalant such as polyphosphate, as knownin the art. It should be appreciated that the filter package 331 is insome embodiments not required and may not be present.

The RO module 170 comprises the tank 350, the RO-pump 450 and theRO-device 301. A RO-device 301 has already been described in detail withreference to the FIG. 5 and reference is made to that description forfurther explanation. The filtered (or unfiltered) feed water enters thetank 350, for example from an upper part of the tank 350. Feed water isaccumulated in the tank 350 and pumped by the RO-pump 450 to the feedinlet 301 a (see FIGS. 5-7) of the RO-device 301.

Empty, low and high-level switches 350 a, 350 b, 350 c provided in tank350 detect its water level, while a computer program run on a controlunit 112 of water purification apparatus 300 is configured to controlthe opening and closing of inlet valve 332 and tank valve 328, which areopen during the filling of tank 350, and closed when the water level intank 350 activates its high-level switch 350 c connected to control unit112. Inlet valve 332 opens again when the water level falls belowlow-level switch 350 b of tank 350, thus tripping the low-level switch350 b connected to control unit 112. If the water level in the tank 350rises too high, excess water is drained via a tank air vent line 325 andtank air vent 335 (overflow connection), e.g. to a tray 420 or drain339. The tank air vent 335 is accessible from outside the waterpurification apparatus 300. The tank air vent 335 may be closed e.g.during transport of the water purification apparatus 300, such that anywater in the tank 350 will be prevented to flow to the tray 420 andcause water to flow out of the water purification apparatus 300.

The control unit 112 is configured to cause RO-pump 450 to stop pumping,if empty level switch 350 a in tank 350 detects air or a critically lowwater level. RO-pump 450 is configured to provide the water flow andpressure requisite for the reverse osmosis process taking place atRO-device 301. As previously described e.g. with reference to FIG. 5,the RO-device 301 filters water to provide purified water at itspermeate outlet 301 b. Reject water leaving RO-device 301 at a rejectoutlet 301 c (may be fed back into RO-pump 450 to conserve waterconsumption or alternatively be pumped to drain 339.

Purified water leaving the RO-device 301 is transported in a purifiedfluid path 371 inside the water purification apparatus 300 before beingoutput through a product port 128, thus a water outlet. The purifiedfluid path comprises permeate fluid path 371 a, polisher fluid path 371b and product fluid path 371 c. The EDI-device 306 may be by-passed viathe bypass path 371 d. The bypass path 371 d is connected to the fluidpath upstream the EDI-device 306, and to the fluid path downstream theEDI-device 306. Purified water leaving the RO-device 301 passes a flowsensor 410, a heater 302, and a permeate temperature sensor 303,included in the permeate fluid path 371 a. The flow sensor 410 monitorsthe flow of the purified fluid leaving the RO-device 301. The heater302, heats, by control of the control unit 112, the purified waterleaving the RO-device 301. The permeate temperature sensor 303 monitorsthe temperature of the purified fluid leaving the RO-device 301 directlydownstream the heater 302. An additional conductivity sensor 304monitors the conductivity of purified water leaving RO-device 301.

Downstream the heater 302, the permeate temperature sensor 303 and theadditional conductivity sensor 304, the purified fluid enters thepost-treatment module 180 via the polisher fluid path 371 b. Thepost-treatment module 180 comprises the polisher device, e.g. theEDI-device 306. The three-way valve 305 c is arranged to be controlledby the control unit 112 to selectively direct the purified fluid flowinto either the EDI-device 306, or into the bypass path 371 d in orderto bypass the EDI-device 306. When directed to the EDI-device 306, thepurified fluid enters the product channel 306 a, the concentrate channel306 b and the electrode channel 306 c of the EDI-device 306. Thepurified fluid is fed to all the channels via the polisher fluid path371 b downstream the three-way valve 305 c. The EDI-device 306 isconfigured to produce product water. The produced product water leavesthe EDI-device 306 and enters the product fluid path 371 c. A productchannel valve 307 regulates the flow rate of the product water in theproduct fluid path 371 c from the product channel 306 a. The concentratefluid path 377 c is arranged to pass concentrate water and the electrodefluid back to the tank 350.

The product water is passed to the product port 128, and further into athereto connected water line 64 (64 a, 64 b) of the fluid line set 40for transport to the point of care. The fluid line set 40 comprises twosterile sterilization filters 70 a, 70 b. The sterile sterilizationfilters 70 a, 70 b filter the product water leaving the product port 128into sterilized product water, that is suitable for injection. Accordingto some alternative embodiments those filters are left out or the numberof filters is less or more than two.

A drain port 118 defines a first drain path 384 to the drain 339. Adrain line 56 of the fluid line set 40 is connected to the drain port118, in order to pass fluid, such as used PD-fluid, from the drain port118 to the drain 339. The first drain path 384 here embodies the part ofa cycler drain path that is present inside the water purificationapparatus 300. The first drain path 384 comprises a conductivity sensor336, a drain path temperature sensor 315 and a drain line valve 341. Theconductivity sensor 336 is configured to measure the conductivity of thefluid in the drain path. The temperature sensor 315 is arranged tomeasure the temperature of the fluid in the first drain path 384. Thedrain line valve 341 is, by control of the control unit 112, arranged toregulate the flow in the first drain path 384 through the conductivitysensor 336. The first drain path 384 further comprises a bypass path 384a arranged to by-pass the conductivity sensor 336, the drain pathtemperature sensor 315 and the drain line valve 341. The bypass path 384a comprises a valve 340. The valve 340 is arranged to regulate the flowthrough the bypass path 384 a.

The flow control device 305 a is configured to control the flow rate ofpurified water in the recirculation path 315 arranged from a pointdownstream the heater 302, the permeate temperature sensor 303 and theadditional conductivity sensor 304, and back to the tank 350. A productwater pressure sensor 308 is arranged to monitor the pressure in theproduct fluid path 371 c downstream the EDI-device 306. A product waterflow sensor 309 is arranged to monitor the flow rate of the productwater downstream the EDI-device 306. The pressure and the flow rate ofthe product water are feed to the control unit 112. The control unit 112is configured to control the operation of the flow control device 305 a.More particularly the control unit is configured to regulate the flowrate in the recirculation path 375 based on the pressure and flow rateof the product water, in order to control the flow rate of the productwater to a desired flow rate, and the pressure of the product water to adesired pressure. The flow control device 305 a is for example amotorized flow control valve that is configured to finely regulate theflow rate in the recirculation path 375.

A product water valve 305 d is arranged to, by control of the controlunit 112, control the produced product flow to go to either the productport 128, or back to the tank 350 via an additional recirculation path,here a first recirculation path 381. An emptying valve 396 is arrangedto control the flow rate in the first recirculation path 381. The firstrecirculation path 381 is fluidly connected to the product fluid path371 c via an air-trap chamber 319. A product water conductivity sensor312 is arranged to monitor the conductivity of the product waterupstream the air-trap chamber 319. A product fluid temperature sensor313 is configured to monitor the temperature of the product waterupstream the air-trap chamber 319.

In operation, a portion of the rejected water leaving the RO-device 301via a fluid path 385 a passes an auxiliary constant flow device 318,which provides a steady flow of rejected water to a three-way valve 305b (e.g. a three-way solenoid valve) under control of control unit 112. Aremaining portion of the rejected water returns to RO-pump 450 via avalve 320 (e.g., a manual needle valve) in a first reject path 385 b.Three-way valve 305 b is configured to selectively divert the rejectedwater either to drain 339 via a second drain path 388 or back to tank350 via a second reject path 389. A bypass-path 385 f is arranged tobypass the auxiliary constant flow device 318. A reject bypass valve 321is arranged to control the flow in the bypass path 385 f by control ofthe control device 112.

All meters and sensors described in connection with water purificationapparatus 300 in FIG. 13 are in some embodiments configured to sendtheir corresponding signals to control unit 112.

The water purification apparatus 300 includes a container 392 containinga microbiological growth inhibiting agent. As illustrated, container 392is in fluid communication with an inlet 392 a of the water purificationapparatus 300. In FIG. 13, the chemical intake path 382 connectscontainer 392 to the fluid path of the water purification apparatus 300.Alternatively, container 392 may be connected via a line (notillustrated) leading directly to disposable cassette 42 operating withcycler 20, or be connected to water line 64, or be connected to drainline 56.

The agent inhibiting microbiological growth in the container 392 may bea suitable physiologically safe acid, such as citric acid, citrate,lactic acid, acetic acid, or hydrochloric acid (or a combinationthereof). In one embodiment, container 392 contains citric acid, citrateor a derivative thereof. It is noted that container 392 may also includeadditives provided together with the acid (such as with citric acid).The chemical inlet 392 a, is located for example at the front of waterpurification apparatus 300. A presence sensor (not shown, e.g. anoptical sensor) is arranged to sense when the container 392 is connectedto the chemical inlet 392 a. The three-way valve 317, under control ofcontrol unit 112, at chemical inlet 392 a is arranged to open towards asecond pump 316 being a chemical intake pump and tank 350. The secondpump 316 is arranged to feed disinfecting solution into tank 350. Theoptical sensor is arranged to detect if the source of cleaning ordisinfection solution is connected or disconnected. If/when thecontainer 392 is removed or is not detected by the optical sensor, thesecond pump 316 is stopped or not activated and three-way valve 317 isclosed towards the chemical inlet 392 a. Three-way valve 317 undercontrol of control unit 112 may also be used to recirculate water anddisinfectant from and to tank 350 during the phases of chemicaldisinfection (i.e. disinfection with a cleaning agent), cleaning and/orrinse. The second pump 316 and a valve 310 are arranged in a path 379fluidly connecting the three-way valve 317 and the product fluid path371 c. The valve 310 is arranged to control the flow in the path 379. Inone embodiment, when the first recirculation path 381 is disinfected forexample during a complete disinfection, the heated fluid is also passedthrough a path 386 between the first recirculation path 381 and thethree-way valve 317, through the path 379 and to the recirculation path381. During this flow the second pump 316 is active and thus pumps theheated fluid to not stop the flow.

In a more detailed disinfection phase example, when chemicaldisinfection is initiated, the level in tank 350 is adjusted to a leveljust above low-level switch 350 b. Control unit 112 causes RO-pump 450to start and run until empty-level switch 350 a indicates a presence ofair. RO-pump 450 is then stopped and inlet valve 332 is opened. Inletvalve 332 is maintained open until empty-level switch 350 a indicateswater. Second pump 316 is then run until a preset amount of chemicalsolution is metered into tank 350. When the level in tank 350 reaches apre-determined level, the three-way valve 317 is opened to drain 339.RO-pump 450 circulates the fluid in the fluid path during the chemicalintake phase and may be operated in two directions to create turbulentflow and to increase disinfection time and contact. At the end of theintake phase, reject bypass valve 321 is opened and the three-way valve305 b is actuated to open second drain path 388 to drain 339 and todrain the water level in tank 350 to its low-level at low level switch350 b.

The described pre-treatment module 160, the RO module 170 andpost-treatment module 180, are enclosed inside of a single waterpurification cabinet 110 a, except for the filter package 331, which isremovably arranged, e.g. hinged, on the outside of the single waterpurification cabinet 110 a. The filter package 331 may then be exchangedwhen exhausted. In an alternative embodiment, the modules may bearranged in separate units. As mentioned above, purified water is sentfrom water purification apparatus 300 to disposable set 40 via waterline 64. Referring to FIG. 1, water line 64 feeds purified water to awater port 282 of cassette 42 of disposable set 40. Water line 64 is inone embodiment a flexible tube having a first end connected to theproduct port 128 of the water purification apparatus 300 and a secondend connected to a water port 282 of the cycler 20. Water line 64 may beat least 2 meters long and in one embodiment longer than 4 meters. Waterline 64 allows water purification apparatus 300 to be installed in aroom having an available water source, while cycler 20 resides in adifferent room in which the patient resides, e.g., sleeps. Water line 64may accordingly be as long as necessary to connect water purificationapparatus 300 to cycler 20.

FIG. 13 also illustrates that the disposable line set 40 includes adrain line 56 configuration arranged to conduct fluid, such as useddialysis fluid, to the drain 339 of the water purification apparatus300. Drain line 56 is e.g. a tube having a first end connected tocassette 42 of cycler 20 and a second end including a drain lineconnector 58 (FIG. 1) connected to a drain port 118 of the waterpurification apparatus 300. Drain line 56 may alternatively be aflexible tube, which may be more than 2 meters long and in someembodiments longer than 4 meters. Drain line may be as long as necessaryto connect between water purification apparatus 300 and cycler 20. Waterline 64 and drain line 56 in the illustrated embodiment run parallelusing dual lumen tubing. It is also possible that water purificationapparatus 300 and cycler 20 are positioned close together, such that thesame two line fluid path including water line 64 and drain line 56 mayfor example be less than 0.5 meters. Moreover, while a dual lumen waterline 64 and the drain line 56 are illustrated, it is possible that waterline 64 and drain line 56 are separate.

A water tray 420 is positioned below the water purification apparatus300. A liquid sensor 370 is arranged at the bottom of the water tray 420to detect any leakage from the water purification apparatus 300. In oneexample embodiment, the water tray 420 is enclosed inside thepurification cabinet 110 a of the water purification apparatus 300.

FIG. 14 illustrates a heat conserving arrangement 500 according to oneexample embodiment. The heat conserving arrangement 500 is arranged totransfer thermal energy, i.e. heat, from the fluid in the first drainpath 384 and/or the fluid in the second drain path 388, to anothermedium such as the fluid in the pre-treatment fluid path 390. Therebythermal energy from the drained fluid is conserved to the water in thepre-treatment fluid path 390, and less energy is needed for anysubsequent heating of the water for heat disinfection, provide a certaintemperature of the product water or providing a constant temperature ofthe RO-membrane. The heat conserving arrangement 500 comprises a heatconserver 501, a first path 502 a, a second path 502 b, a third path 503a and a fourth path 503 b. A three-way valve 502 c is arranged to, undercontrol of the control unit 112, direct water from the feed fluid path391 to the heat conserver 501 via the first path 502 a. A second path502 b directs heated water from the heat conserver 501 back to the feedfluid path 391. A three-way valve 503 c is arranged to, by control bythe control unit 112, direct fluid from any of the drain paths 384, 388to the heat conserver 501 via the third path 503 a. A fourth path 503 bdirects cooled fluid from the heat conserver 501 back to drain paths384, 388, and further to drain 339.

Alternatively, the heat conserving arrangement 500 is arranged totransfer thermal energy, i.e. heat, from the fluid in the first drainpath 384 to the reject fluid from the RO-device 301 in any of the fluidpath 385 a, the second drain path 388, the first reject path 385 b, orthe second reject path 389, or to the fluid in the tank 350, or to thefeed fluid in the feed fluid path 391. In one embodiment, the seconddrain path 388 is arranged as a cooling coil around part of the firstdrain path 384 inside the apparatus 300. In another embodiment, thereject fluid that is passed to drain 339 via the second drain path 388is guided via a further line fluidly connected to the second drain path388 to the conserving arrangement 500 and thereafter via another line tothe fluid in the pre-treatment fluid path 390. A valve may control theflow in the second drain path 388 downstream the connection to the linethat guides reject fluid to the conserving arrangement 500, and anothervalve may control the flow in the further line that guides reject fluidto the pre-treatment fluid path 390.

Optionally, a fan may be arranged to further cool the reject fluid flowleaving the apparatus 300 via the second drain path 388 and/or the drainfluid leaving the apparatus via the first drain path 384.

The heat conserver 501 comprises for example a passive or active heattransfer element, e.g. a heat exchanger or a Peltier element. In oneembodiment, the heat conserver 501 comprises a conserving element, e.g.a closed container or fluid path with another medium such as anotherfluid, which absorbs the heat and thus thermal energy from the fluid inany of the drain paths 384, 388. The absorbed thermal energy may betransferred to the fluid in the pre-treatment fluid path, 390 or thereject fluid at any time, or be released to the surroundings. In oneembodiment, the heat conserver 501 comprises a fluid accumulator wheresome of the fluid from any of the drain paths 384, 388 is collected, forfuture transfer of heat from the fluid to the water in the feed fluidpath 391 or the first reject path 385 b. The closed container and thefluid accumulator are in one embodiment insulated in order to preventheat loss. For example, they may be insulated in order to keep the heatfor up to 24 h with minimal loss. The heat can then be used for heatingup the water in the pre-treatment fluid path 390 in the next treatmentsaving energy, or simply released to the surroundings. Further, ifthermal energy in the drain fluid is reduced the drained fluid willbecome less hot, which reduces the risk for the operator interactingwith the drain paths 388, 384 to become burnt by the hot drain fluid.The function can be bypassed in phases when it is not used, bycontrolling the three-way valves 502 c, 503 c. The second path 502 b andthe fourth path 503 b in some embodiments include valves (not shown),controllable by the control unit 112, to restrict the flows in the same.The heat conserving arrangement 500 may be included inside the cabinet110 a of the water purification apparatus 300. According to anotherembodiment, the heat conserving arrangement 500 is arranged outside thecabinet 110 a of the water purification apparatus 300.

The present disclosure is not limited to the above-described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the disclosure, which is defined by the appending claims.

1-36. (canceled) 37: A water purification apparatus for producingpurified water, the water purification apparatus comprising: a reverseosmosis device arranged to produce a purified fluid flow and a rejectfluid flow, the reverse osmosis device comprising a feed inlet, apermeate outlet and a reject outlet, a feed fluid path arranged with areverse osmosis pump to pump feed fluid to the feed inlet, a heaterarranged to heat the purified fluid produced by the reverse osmosisdevice downstream the reverse osmosis device, a first fluid patharranged to circulate heated purified fluid from a point downstream theheater to a tank arranged in the feed fluid path inside the waterpurification apparatus, a second fluid path arranged to transport theheated purified fluid inside the water purification apparatus; a valvearrangement arranged to direct the heated purified fluid into the firstfluid path or the second fluid path, and a control unit configured tocontrol cleaning of the water purification apparatus, the control unitbeing configured to cause the water purification apparatus to: controlheating, with the heater, of the purified fluid from the reverse osmosisdevice, control the valve arrangement to re-circulate the heatedpurified fluid in the first fluid path until a first temperaturedependent criterion is fulfilled, control the valve arrangement tore-direct the heated purified fluid to flow in a second fluid path ofthe water purification apparatus in response to the first temperaturedependent criterion is fulfilled, and control heating, with the heater,of the re-directed heated purified fluid in order to fulfill a secondtemperature dependent disinfection criterion for the second fluid path.38: The water purification apparatus according to claim 37, wherein thefirst temperature dependent criterion is a first temperature dependentdisinfection criterion. 39: The water purification apparatus accordingto claim 37, further comprising a first temperature sensor arranged tomeasure a temperature of the purified fluid in the first fluid path, andwherein the first temperature dependent criterion includes a temperatureof the purified fluid being within a range of 70°-95° Celsius. 40: Thewater purification apparatus according to claim 39, further comprising afirst flow sensor arranged to measure a flow rate of the purified fluid,and wherein the first temperature dependent criterion includes thepurified fluid obtaining a predetermined temperature dependent flowrate. 41: The water purification apparatus according to claim 37,further comprising a second temperature sensor arranged to measure atemperature of the purified fluid in the second fluid path, and whereinthe control unit is configured to determine, based on the measuredtemperature, a time duration for heat disinfecting the second fluid pathwith the purified fluid at the measured temperature such that abacterial reduction criterion is fulfilled, and control heatdisinfection of the second fluid path based on the time duration tofulfill the bacterial reduction criterion. 42: The water purificationapparatus according to claim 37, further comprising a port in fluidcommunication with the second fluid path, the port being arranged to beconnected to a fluid line set, and wherein the second temperaturedependent disinfection criterion includes a temperature dependentdisinfection criterion for the port. 43: The water purificationapparatus according to claim 37, wherein the second fluid path includesa first drain path, and wherein the second temperature dependentdisinfection criterion is a temperature dependent disinfection criterionfor the first drain path. 44: The water purification apparatus accordingto claim 37, wherein the first fluid path or the second fluid pathincludes a polisher device, and wherein the control unit is configuredto cause the water purification apparatus to: control heating of thepurified fluid that flows through the polisher device such that atemperature dependent disinfection criterion for the polisher device isfulfilled, and control the water purification apparatus to bypass thepolisher device in response to the temperature dependent disinfectioncriterion for the polisher device being fulfilled. 45: The waterpurification apparatus according to claim 37, wherein the control unitis configured to cause the water purification apparatus to control afluid level in the tank to a predetermined level of the tank, beforeheating of the purified fluid. 46: The water purification apparatusaccording to claim 37, wherein the control unit is configured to causethe water purification apparatus to: control the reverse osmosis pump topump water from a water source to the reverse osmosis device until apredetermined cooling criterion for a reverse osmosis membrane of thereverse osmosis device has been fulfilled, and control the valvearrangement to drain reject fluid from the water purification apparatus.47: The water purification apparatus according to claim 37, wherein thewater purification apparatus includes a second pump, and wherein thecontrol unit is configured to cause the water purification apparatus to:control the second pump to pump air, and control the valve arrangementto direct the air past a closed port of the water purification apparatusin order to remove water from the port. 48: The water purificationapparatus according to claim 37, wherein the water purificationapparatus includes a second pump arranged for pumping a cleaning agent,and wherein the control unit is configured to cause the waterpurification apparatus to: control the second pump to pump the cleaningagent into the feed fluid path, and circulate the cleaning agent in areject recirculation path from the reject outlet to the feed inlet, inorder to remove scaling on a reverse osmosis membrane of the reverseosmosis device. 49: The water purification apparatus according to claim37, wherein the permeate fluid path is arranged such that it is incontact with the heater in order to heat the purified fluid produced bythe reverse osmosis device. 50: The water purification apparatusaccording to claim 37, further comprising a heat conserving arrangementarranged to transfer heat to another medium from at least one of a fluidin a first drain path and a fluid in a second drain path. 51: The waterpurification apparatus according to claim 37, further comprising adisposable line set in fluid communication with the water purificationapparatus, and wherein the control unit is configured to cause the waterpurification apparatus to clean the disposable line set. 52: A waterpurification apparatus for producing purified water, the waterpurification apparatus comprising: a reverse osmosis device arranged toproduce a purified fluid flow and a reject fluid flow, the reverseosmosis device comprising a feed inlet, a permeate outlet and a rejectoutlet, a feed fluid path arranged with a reverse osmosis pump to pumpfeed fluid to the feed inlet, a heater arranged to heat the purifiedfluid produced by the reverse osmosis device downstream the reverseosmosis device, a purified fluid path arranged to transport the heatedpurified fluid, a polisher device arranged in the purified fluid path, asecond fluid path arranged to bypass the polisher device and totransport the heated purified fluid past the polisher device, a valvearrangement arranged to direct the heated purified fluid into thepurified fluid path or into the second fluid path, a control unitconfigured to control cleaning of the water purification apparatus, thecontrol unit being configured to cause the water purification apparatusto: control heating, with the heater, of the purified fluid in thepurified fluid path in order to fulfill a temperature dependentdisinfection criterion for the polisher device, re-directing thepurified fluid producing device to bypass the polisher device inresponse to the temperature dependent disinfection criterion for thepolisher device being fulfilled, and control heating, with the heater,of the purified fluid in the second fluid path in order to fulfill atemperature dependent disinfection criterion for the second fluid path.53: The water purification apparatus according to claim 52, wherein thesecond fluid path includes at least one of: a port in fluidcommunication with the second fluid path, the port being arranged to beconnected to a fluid line set, wherein the second temperature dependentdisinfection criterion is a temperature dependent disinfection criterionfor the port, and a first drain path, wherein the second temperaturedependent disinfection criterion is a temperature dependent disinfectioncriterion for the first drain path. 54: The water purification apparatusaccording to claim 52, wherein the permeate fluid path is arranged suchthat it is in contact with the heater in order to heat the purifiedfluid produced by the reverse osmosis device. 55: A method for cleaninga water purification apparatus configured to produce purified water, thewater purification apparatus including a reverse osmosis deviceconfigured to produce a purified fluid flow and a reject fluid flow, themethod comprising: controlling heating of purified fluid in the purifiedfluid flow downstream the reverse osmosis device, re-circulating theheated purified fluid in a first fluid path from a point downstream theheater to a tank arranged in a feed fluid path upstream the reverseosmosis device until a first temperature dependent criterion isfulfilled, re-directing the heated purified fluid to flow in a secondfluid path of the water purification apparatus in response to the firsttemperature dependent criterion being fulfilled, and controlling heatingof the re-directed heated purified fluid such that a second temperaturedependent disinfection criterion for the second fluid path is fulfilled.56: The method according to claim 55, wherein the first temperaturedependent criterion is a first temperature dependent disinfectioncriterion. 57: The method according to claim 55, wherein controllingheating of purified fluid and re-circulating the heated purified fluidincludes measuring a temperature of the purified fluid in the firstfluid path, and wherein the first temperature dependent criterionincludes a temperature of the purified fluid being within a range of70°-95° Celsius. 58: The method according to claim 57, whereincontrolling heating of purified fluid and re-circulating the heatedpurified fluid includes measuring a flow rate of the purified fluid, andwherein the first temperature dependent criterion includes the purifiedfluid obtaining a predetermined temperature dependent flow rate. 59: Themethod according to claim 55, wherein controlling heating of there-directed heated purified fluid includes measuring the temperature ofthe fluid in the second fluid path, and wherein the method furthercomprises: determining, based on the measured temperature, a timeduration for heat disinfecting the second fluid path with the purifiedfluid at the measured temperature such that a bacterial reductioncriterion is fulfilled, and controlling heat disinfection of the secondfluid path based on the time duration to fulfill the bacterial reductioncriterion. 60: The method according to claim 55, wherein the waterpurification apparatus comprises a port in fluid communication with thesecond fluid path, the port being arranged to be connected to a fluidline set, and wherein the second temperature dependent disinfectioncriterion includes a temperature dependent disinfection criterion forthe port. 61: The method according to claim 55, wherein the second fluidpath includes a first drain path, and wherein the second temperaturedependent disinfection criterion is a temperature dependent disinfectioncriterion for the first drain path. 62: The method according to claim55, wherein the first fluid path or the second fluid path includes apolisher device, and wherein the method comprises: controlling heatingof the purified fluid that flows through the polisher device such that atemperature dependent disinfection criterion for the polisher device isfulfilled, and controlling the water purification apparatus to bypassthe polisher device in response to the temperature dependentdisinfection criterion for the polisher device being fulfilled. 63: Themethod according to claim 55, further comprising controlling a fluidlevel in the tank to a predetermined level of the tank, before heatingof the purified fluid. 64: The method according to claim 55, furthercomprising: pumping water from a water source to the reverse osmosisdevice until a predetermined cooling criterion for a reverse osmosismembrane of the reverse osmosis device has been fulfilled, andcontrolling the valve arrangement to drain reject fluid from the waterpurification apparatus. 65: The method according to claim 55, furthercomprising pumping air past a closed port of the water purificationapparatus in order to remove water from the port. 66: The methodaccording to claim 55, further comprising circulating a cleaning agentin a reject recirculation path from a reject outlet of the reverseosmosis device to a feed inlet of the reverse osmosis device, in orderto remove scaling on a reverse osmosis membrane of the reverse osmosisdevice. 67: The method according to claim 55, further comprisingtransferring heat to another medium from at least one of a fluid in afirst drain path and a fluid in a second drain path. 68: The methodaccording to claim 55, further comprising cleaning a disposable line setin fluid communication with the water purification apparatus. 69: Amethod for cleaning a water purification apparatus configured to producepurified water, the water purification apparatus including a reverseosmosis device configured to produce a purified fluid flow and a rejectfluid flow, the method comprising: controlling heating of the purifiedfluid produced by the reverse osmosis device downstream the reverseosmosis device, directing the heated purified fluid in a first fluidpath, through a polisher device, re-directing the heated purified fluidinto a second fluid path to bypass the polisher device in response to atemperature dependent disinfection criterion for the polisher devicebeing fulfilled, and controlling heating of the re-directed purifiedfluid in order to fulfill a temperature dependent disinfection criterionfor the second fluid path. 70: The method according to claim 69, whereinat least one of: the water purification apparatus includes a port influid communication with the second fluid path, the port being arrangedto be connected to a fluid line set, and wherein the second temperaturedependent disinfection criterion is a temperature dependent disinfectioncriterion for the port, and the second fluid path includes a first drainpath, and the second temperature dependent disinfection criterion is atemperature dependent disinfection criterion for the drain path. 71: Anon-transitory, computer-readable medium storing instructions, whichwhen executed by a processor, cause the processor to: control heating ofpurified fluid in a purified fluid flow downstream a reverse osmosisdevice in a water purification apparatus, re-circulate in the waterpurification apparatus the heated purified fluid in a first fluid pathfrom a point downstream a heater to a tank arranged in a feed fluid pathupstream the reverse osmosis device until a first temperature dependentcriterion is fulfilled, re-direct the heated purified fluid to flow in asecond fluid path of the water purification apparatus in response to thefirst temperature dependent criterion being fulfilled, and controlheating of the re-directed heated purified fluid such that a secondtemperature dependent disinfection criterion for the second fluid pathis fulfilled.